Francis Bacon was a major figure in the seventeenth-century movements to reform knowledge and build a new conception of nature different from the largely Aristotelian conceptions that then dominated the universities. In his Novum organum (1620), De augmentis scientiarum (1623), and the Sylva Sylvarum (1626/27), among many other writings, Bacon outlined a program that involved a careful analysis of the ways in which people are prone to error (the “four Idols”), a method for collecting and arranging observations and experiments into natural histories, and using them to build natural philosophies that would enable people to control nature. While Bacon’s place in the Dutch intellectual world has not been studied as carefully as that of Descartes, he was, nevertheless, a significant influence on those interested in natural history and natural philosophy in the Low Countries. While not a major influence on Spinoza, Bacon left his mark in interesting ways. Only one book by Bacon appears in Spinoza’s library at the time of his death (a Latin translation of Bacon’s Essays). However, there are a number of direct citations and allusions to him in Spinoza’s work.

In the very first surviving exchange of letters between Henry Oldenburg, important as secretary to the Royal Society of London, and Spinoza, Oldenburg reminds Spinoza of their discussions of Bacon (along with Descartes) in Rijnsburg and asks him his views on Bacon’s defects. Spinoza answers with a clear allusion to the doctrine of the Idols in Novum organum i.38–68, explaining briefly why he dismisses Bacon’s views on the infirmities of the mind (Ep2, iv/8–9). As Spinoza reads Bacon, he is mistaken about the true nature of the human mind and the cause of error, attributing it largely to the inherent imperfections of the mind, and to the misuse of the will.

However, Spinoza seems to have a much more positive view of the method of the Novum organum. Though he doesn’t mention Bacon explicitly, Spinoza clearly models his method of interpreting Scripture in TTP7 on Bacon’s method for interpreting nature:

This seems to be a direct allusion to the inductive method in Novum organum ii.10–20, which Bacon explicitly calls the “interpretation of nature” throughout the work. (Spinoza makes another positive allusion to Baconian method in Ep37, iv/188–89.) “History” here is understood as a collection of empirical observations. Spinoza sometimes uses “history” in this way in his writings (DPP pref. [G I 226], TTP15[25]). Bacon often contrasts this disciplined use of experience in the method with what he calls “random experience” or “experientia vaga” (Novum organum i.100), a term that Spinoza also seems to have borrowed from him (TIE[19–20, 75]; E2p40s2).

Pieter Balling was the recipient of Ep17, written in Voorburg on July 20, 1664, a moving attempt on the part of Spinoza to console Balling after the recent loss of a child. The two must have been intimate friends. Ep17 refers to a previous letter, in which Balling had informed Spinoza about his grief, and it seems likely a regular correspondence originated between the two, following Spinoza’s departure from Amsterdam. Apparently the editors of the OP decided to leave the other letters unpublished. Balling’s prominence in Spinoza’s Amsterdam circle of friends is borne out by the fact that he translated Spinoza’s debut on the philosophy of Descartes into Dutch, and indications are that he was mainly responsible for the first two parts of Jan Glazemaker’s Dutch translation of the Ethics.

Balling’s date of birth is unknown; he passed away in Amsterdam in December 1664. He was a prosperous grocer, in a position to pursue his theological and philosophical interests. Two years before he died, he was the anonymous author of a short treatise, titled Het Licht op den Kandelaar, in which a number of literal quotes from Spinoza’s KV occur, which by this time must have circulated among some of Spinoza’s closest friends. Balling wrote Het Licht following William Ames’s critique of Galenus Abrahamsz de Haan, one of the more liberal leaders of the Amsterdam Mennonites. Ames was one of the Quakers who had settled in the Dutch Republic during the early 1650s. Initially, they appear to have been struck by their affinity to local Mennonites, but soon tensions arose. Balling’s response to Ames, however, was appreciated by Quakers, and an English translation, The Light upon the Candlestick, produced by the Rotterdam Quaker Benjamin Furly, was included at the end of William Sewell’s History of the Quakers (Reference Sewell1722).

Balling’s text leaves room for a variety of interpretations, arguing as it does that people are best advised to follow their inner light, the principle of all knowledge and religion. This inner light is not only specified as being identical to “Reason,” but it is also termed “Christ” and “The Truth.” It would seem, then, that Balling had aimed to accentuate what Mennonites and Quakers had in common rather than to put Ames in his place. In 1684 a second edition was published, together with Jarig Jelles’s Belijdenisse.

With Jelles and Simon Joosten de Vries, Balling was part of the tolerant faction of the hopelessly divided Mennonite community of Amsterdam. Balling played a prominent part in the so-called Lammerenkrijgh (War of the Lambs) that tore the community apart during the early 1660s. Dozens of pamphlets were produced. Joining the fray, he wrote two detailed pleas in favor of toleration among its members in which he seriously questioned the authority of its leaders. According to Balling, the freedom of individual believers as well as their mutual equality should be respected by their ministers.

Pierre Bayle was a French Huguenot philosopher and founding editor of the journal Nouvelles de la République des Lettres. His principal work, the Dictionnaire historique et critique, was a massive encyclopedia, whose extensive article on Spinoza was of both historical and philosophical importance. Historically, Bayle’s painstaking research into the details of Spinoza’s life and works made the article an indispensable source of information concerning the Dutch philosopher. Philosophically, the article featured one of the earliest and most influential critical engagements with Spinoza’s metaphysical system, a reading that would shape the reception of Spinoza’s work throughout much of the eighteenth century. In addition, Bayle’s portrayal of Spinoza as the exemplar of the virtuous atheist enjoyed great currency among Enlightenment thinkers and, in particular, the French philosophes.

Bayle’s critical remarks are largely confined to Part 1 of the Ethics, and in particular, to Spinoza’s monism, pantheism, and necessitarianism. Bayle interprets the central concepts of Spinoza’s substance ontology along broadly Cartesian lines. The heart of Bayle’s critique is aimed at Spinoza’s substance monism, which he understands as the view that God is the unique substance in which all finite beings inhere as modes. Bayle’s principal criticism concerns the attribute of Extension, which he understands to be the physical, extended plenum considered in general. According to Bayle it is the very nature of Extension to be composite – that is, to consist of really distinct parts, each of which is itself a substance. Now because Spinoza, following Descartes, held that there is only a distinction of reason between a substance and its attribute, it follows that God himself must be composite or composed of a multiplicity of substances. Bayle bolsters this argument with the principle that incompatible modes require distinct subjects of inherence, contrary once again to Spinoza’s claim that God is the unique and indivisible substance.

Bayle further argues that Spinoza cannot secure divine immutability. According to Bayle, Spinoza’s God is subject to change in so far as ordinary objects – rivers, plants, animals, etc. – are modes that inhere in the unique substance. Now because what it is for a substance to change is to gain or lose a certain quality or mode while the underlying essence remains the same, it follows that wherever there is a succession of modes, Spinoza’s God undergoes change. Bayle acknowledges that Spinoza claims only that God’s existence and attributes are unchangeable (“God, or all of God’s attributes, are immutable,” E1p20c2). However, he complains that this amounts to a confusion between change and annihilation, so that Spinoza has shown only that God cannot be annihilated.

In addition, Bayle briefly raises an important objection concerning the numerical distinctness of God’s attributes. As noted above, Bayle takes Spinoza to hold that “the attribute of a substance does not differ actually from that substance” (Bayle Reference Bayle and Popkin1991, 259), but to claim nevertheless that the unique substance consists of an infinite number of attributes. However, given the logical truth that “two things identical to a third are identical to one another,” it follows that each of God’s attributes, and in particular Thought and Extension, must be identical, which Bayle takes to be both absurd on its face and in violation of their conceptual independence (Bayle Reference Bayle and Popkin1991, 308n96).

Though frequently polemical – even derisive – in tone, Bayle’s article offers at times a surprisingly sophisticated critique of Spinoza’s substance monism, one whose influence would be felt well into the eighteenth century. Hume’s portrayal of Spinoza’s unique substance in the Treatise as a simple, indivisible subject in which ordinary objects inhere is drawn directly from Bayle, as are the three objections to Spinoza’s system that Hume claims bear equally on the simple, immaterial soul posited by orthodox theologians. Voltaire, in Le philosophe ignorant, echoes the pantheistic reading offered by Bayle and defends the soundness of Bayle’s critique against the charge of having misunderstood Spinoza’s system. Perhaps more tellingly, the long entry on Spinoza in the Encyclopédie is little more than a close paraphrase of the central passages of Bayle’s article (Diderot and d’Alembert Reference Diderot and d’Alembert1751).

Among contemporary scholars, Bayle’s interpretation of Spinoza’s monism continues to be a subject of debate. Curley’s (Reference Curley1969) denial that the relation of mode to substance is to be understood as inherence is motivated in part by the unacceptable consequences that Bayle attempted to draw from Spinoza’s ontology when read along Cartesian lines. On the other hand, many of those who defend the inherence interpretation have striven to show that the consequences to which Bayle draws attention do not, in fact, follow. Bennett (Reference Bennett1984), for example, attempts to explain how finite material objects can be adjectival on extended substance while avoiding the worry that an indivisible substance cannot be the subject of incompatible properties.

While modern scholars have by and large rejected Bayle’s criticisms, explaining precisely where he goes wrong is still taken by many to be an important task (Melamed Reference Melamed2013b). In this sense, perhaps Bayle’s most lasting contribution to Spinoza scholarship is to have raised many of the central interpretive difficulties that continue to exercise commentators.

Since Spinoza did not write in English, he did not use the term “belief.” Accordingly, it is a matter of interpretative choice (and of some debate) which bits of his philosophy, if any, are best understood in terms of beliefs. Spinoza’s own terms for doxastic states that are the most natural candidates for being translated as “belief” are, in Latin, “opinio,” “cognitio,” the verb “credere,” or even the terms “iudicium” and “idea,” as well as “geloof,” “mening,” and “waan” in Dutch. However, many of these terms are not as epistemically neutral as the English term “belief,” insofar as Spinoza often uses them to designate epistemically deficient doxastic states (such as “opinio” in E2p40s2, or “waan” in KV2.1–2) or epistemically privileged states (such as “(ware) geloof,” which Spinoza uses to designate doxastic states by which “we grasp … that it must be so and not otherwise,” KV2.2).

Given that all doxastic states (of whatever epistemic quality) are constituted by ideas for Spinoza, it seems natural to take beliefs to be closely associated with ideas for Spinoza. This association between ideas and beliefs is also suggested by Spinoza’s view that “an idea, insofar as it is an idea, involves an affirmation or negation” (E2p49s) since affirming or denying ideas are ways of taking a doxastic stance toward these ideas, that is, ways of taking the ideas in question to be true or false, of which belief and disbelief are paradigmatic instances.

Spinoza developed this view about ideas involving their own share of affirmation or negation in direct opposition to Descartes’s “doxastic voluntarism,” according to which our beliefs (that is, our affirmation or denial of ideas) is due to our will. For Spinoza, this position is flawed insofar as it relies on a distorted metaphysical picture of our mind by assuming that we are equipped with a faculty of free will by which it is ultimately up to us to affirm or deny an idea perceived by the intellect. According to Spinoza, there is no such free will to begin with (E1p32) and if we assume otherwise, we do so because we are ignorant of the causes of our volitions and appetites (E1app). What is more, Spinoza also rejects the presupposition that our mind is equipped with a distinctive faculty – the faculty of will – with the help of which we can take a stance on our ideas. This is because our mind is but a bundle of ideas for Spinoza: it consists of the ideas corresponding to the parts of our body (E2p15), and there are no “faculties” somehow standing behind these ideas and causing them. Rather, Spinoza explains, “faculties are either complete fictions or nothing but Metaphysical beings, or universals, which we are used to forming from particulars” (E2p48s). According to this criticism, there are no more mental faculties (like the will and the intellect) over and above certain ideas, which are more or less similar to one another, than there is any ‘stone-ness’ over and above particular bodies, which, due to their mutual similarity, we classify as stones. Hence we should not conceive of faculties like the will as distinctive entities over and above our ideas; as entities that we could appeal to in order to explain why we affirm certain ideas and reject others, as suggested by the doxastic voluntarist (see Curley Reference Curley, Freeman and Mandelbaum1975, Renz Reference Renz2014, and Schmid Reference Schmid, Perler and Corcilius2014, 253–55, for further discussion).

Spinoza’s denial of doxastic voluntarism also plays an important role in his defense of freedom of opinion (TTP20, TP3), as it relies on his view that it is impossible for us to control our ideas at will. As Spinoza argues, given this inability, any attempt to prescribe what people should believe is going to be futile. Or even worse: it will make people turn against the authority that tries to prescribe them what to believe. So, one important reason for granting freedom of opinion according to Spinoza lies in the fact that it is (metaphysically) impossible to enforce any political law about what to think at all.

While it is widely acknowledged that Spinoza opposes Descartes’s voluntarist theory of belief, it is contested what (if anything) Spinoza’s own theory of belief amounts to. In particular, it is debated whether Spinoza’s view that all ideas are intrinsically equipped with their own share of affirmation (or negation) is sufficient for conceiving all of his ideas as beliefs. While this interpretation has been defended by Della Rocca, who holds that for Spinoza all “ideas are beliefs” (Reference Della Rocca2003, 208), other scholars have opted for a more nuanced reading. Diane Steinberg, for instance, has argued for what has aptly been called a “dominance model of belief.” According to this model, only dominant ideas, not all ideas, should be construed as beliefs. A “dominant” idea is an idea that succeeds in determining our actions, and is not prevented from doing so by other, more powerful ideas (Steinberg Reference Steinberg2005, 151). This reading gains support from Spinoza’s account of denial, which he spells out in terms of ideas “excluding” each other: “if the Mind perceived nothing else except the winged horse, it would regard it as present to itself … unless … the imagination of the winged horse were joined to an idea which excluded the existence of the same horse” (E2p49s, see also E2p17s). This suggests that I will only deny an idea with the content p if I have another idea whose content q is incompatible with p. However, if all ideas are beliefs for Spinoza, it seems that I can only deny that p if I believe both q (something incompatible with p) and p. What is more, on this account it seems unclear why I should be seen as denying p as opposed to denying q, since p is just as incompatible with q as q is with p, such that we have equal reason to describe me as denying q. By attributing a dominance model of belief to Spinoza, both problems disappear immediately: I deny p rather than q because only the idea with the content q is a more powerful idea (it determines my behavior) and for the very same reason I only believe q and disbelieve p.

However, construing beliefs as dominant ideas is not unproblematic either. A particularly salient problem is that Spinoza seems to allow for cases in which our actions are dominated by ideas that we would not describe as beliefs. Akrasia (or weakness of will) is a case in point. Spinoza seems to allow for akrasia since he tells us in E4p17s that he can account for the phenomenon captured by “that verse of the Poet: … video meliora, proboque, deteriora sequor [I see and approve the better, but follow the worse].” Accordingly, Spinoza seems to agree that there are situations in which people act against their better judgment (for example on their [imaginative] idea that it would be good to have dessert, even though they believe that going without dessert would be better).

In reaction to such (and other) difficulties, scholars have been pursuing two main strategies. The far more widespread one consists in refining the conditions under which ideas qualify as beliefs for Spinoza. (For example, Steinberg Reference Steinberg2018b distinguishes between two types of strength by which ideas can dominate our actions: doxastic versus affective strength, with only the latter type of strength turning ideas into beliefs). Another (much more radical) strategy consists in denying that Spinoza’s philosophy leaves any room for beliefs at all. A recent example of this strategy is Lin (Reference Lin, Ball and Schuringa2019a, 41–2), who argues that the notion of belief is an essentially normative notion, whose instantiation requires the existence of certain norms (such as the norm that beliefs ought to be formed based on evidence or that they ought to guide our actions). It is questionable whether there is room for such norms (and hence for beliefs) in Spinoza’s philosophy. So, while Spinoza has much to say on ideas and how they determine our cognitive economy and our actions, it is very much a matter of debate which of these insights are best rendered in terms of “beliefs.”

Blessedness (BEATITUDO) is Spinoza’s highest ethical ideal (E4app4, E5p42) and specifying the conditions for its attainment is the primary goal of the Ethics (E2pref, E5pref). In Spinoza’s philosophy, as in biblical theology, blessedness is related to a cluster of concepts: the love of God (E5p42d, TTP4[14]), salvation (E5p36s, TTP7[1]), and true peace of mind (E5p42s, TTP5[8]). In this respect, philosophy and theology have a common end, though Spinoza emphasizes important differences in their accounts of how blessedness is achieved (TTP15[22, 34, 44]).

In philosophy, Spinoza identifies blessedness with the “satisfaction of mind” (animi acquiescentia) that arises from the intuitive knowledge of God (E4app4; cf. TTP7[68]). Spinoza also identifies blessedness with the “intellectual love of God” (E5p33; cf. TTP4[14]; Ep21, iv/127–28), which he claims is identical to “God’s love for men” (E5p36s). The distinctions among these affects reflect the content of intuitive knowledge and the different ways in which a finite mind and God can be regarded as causes of it.

In possessing intuitive knowledge, or “knowledge of the third kind,” we are conscious of God and of the necessary dependence of the essences of singular things on God (E5p25s, E5p42s; cf. E2p40s2, TTP4[10–11]). In achieving this knowledge, we pass to our greatest perfection and experience the greatest joy (E5p27d). Since we are aware of our own virtue, or power, as we experience this joy, we associate it with the idea of ourselves as cause (E5p27d). Conceived in this way, the joy that arises from the third kind of knowledge is “satisfaction of mind” (E5p27, E5p38s).

The idea of ourselves that accompanies the joy arising from intuitive knowledge must be an idea of the mind as eternal; that is, the mind knows itself as “it is in God and is conceived through God” (E5p30). Accordingly, the mind’s self-knowledge must be accompanied by an idea of God through which the mind itself is conceived (E5p32d). It follows that the joy arising from intuitive knowledge is also related to the idea of God as its cause. In this way, we are affected by “intellectual love of God” (E5p32c).

Finally, the mind’s intuitive self-knowledge is nothing but God’s knowledge of himself insofar as he is explained through the human mind (E5p36d). Hence, the love the mind has for God is “part of the infinite love by which God loves himself” (E5p36d). Because our minds are parts of God’s infinite intellect, in loving himself, God also loves human beings. Thus, Spinoza concludes, “God’s love of men and the mind’s intellectual love of God are one and the same” (E5p36c).

Although Spinoza characterizes blessedness as an affect, he issues an important caution about it. Intuitive knowledge belongs to an eternal mind, which cannot increase in perfection and thus does not experience joy, according to Spinoza’s definition. An eternal mind, he emphasizes, “has had eternally the same perfections which, in our fiction, now come to it” (E5p33s; E3DA3exp). Thus, blessedness must be a unique kind of affective state. It is not, like joy, identified with an increase in perfection, but with the very perfection that, in achieving intuitive knowledge, we recognize to define our existence.

Willem van Blijenbergh was a Dutch grain broker who had authored a work condemning atheism and defending revealed religion in 1663, a year before beginning his correspondence with Spinoza. After reading Spinoza’s DPP and CM, he wrote and raised many awkward questions. The correspondence between the two men amounts to eight letters, four from each (Ep18–24, Ep27). Some commentators have suggested that Blijenbergh was obtuse. Although he surely was a frustrating interlocutor (Spinoza’s final letter, requesting him to desist from further correspondence, is a study in polite forbearance), contemporary scholars arguably should be grateful for his dogged persistence which resulted in Spinoza offering uncharacteristically detailed expositions of his views on the problem of evil, free will, sin, and the nature of God. Of course, these four topics are intimately interrelated, as these letters so brilliantly demonstrate.

Traditional Christian theology holds that evil enters the world through a human choice to oppose God’s will. Adam disobeys God, and Adam’s punishment follows. The biblical account of Adam says that he sins through the exercise of his free will; he disobeys the command of God not to eat of the tree of good and evil. Adam interprets his fate (exile from Eden, enforced toil, and mortality) as punishment imposed by an angry God. Spinoza suggests a more adequate framing of Adam’s misfortune would understand it as a bad encounter between Adam and the apple, where the apple acts as a poison when brought into relation with Adam’s body. Adam exemplifies not weakness of will but the inadequacy of human knowledge and our natural disposition to fill gaps in our knowledge with fictions that invert cause and effect (see E1app, ii/80). Against the scriptural view, Spinoza argues that Adam lacks freedom and power and is pitiably ignorant. He is entangled in a web of superstitious beliefs which represent God as experiencing affects, as a judge of human action, and as acting in order to achieve some end. In contrast, according to Spinoza, Adam did not break a commandment and he was not the object of punishment. Rather, his state of privation, after eating the fruit, followed necessarily from the act of eating it, as an effect must follow from a cause. As Spinoza writes to Blijenbergh, “the prohibition to Adam, then, consisted only in this: God revealed to Adam that eating of that tree caused death, just as he also reveals to us through the natural intellect that poison is deadly to us” (Ep19). Adam’s ignorance is compounded insofar as he interprets his act and its consequences in a moral rather than a natural register. That is, he confuses the moral order, which views the act as evil, with the natural order, in which the fruit has debilitating consequences for him. The consequence of the act lies in the relation between his body and the fruit, and the effect of combining his body and the fruit is that he is poisoned. Good, bad, and evil, for Spinoza, are all relational terms he names “beings of reason.”

But what does it mean to say that after eating from the tree of good and evil Adam is deprived of a more “perfect” state, and are we to understand that “good” and “evil” are mere illusions? The way Spinoza explains “perfection” and “privation” results in further puzzlement for Blijenbergh. On Spinoza’s account, “privation” is a human way of grasping changes in an individual, by way of comparing that individual to an ideal, say, a model of the perfect human being, of which Adam falls short. (See E4pref for Spinoza’s description of the wise man, the naturae humanae exemplar). Beings of reason need not be erroneous notions, provided that we recognize their possible ameliorative function and their fictive status. But God does not know things through abstractions, and so does not judge Adam to have sinned, or to be deprived of some previous state (Ep19). For example, where the human intellect may judge a blind man to be deprived of sight, in God’s intellect the blind man no more lacks sight than does a sightless stone. Each individual is known adequately by God in its essence, its singularity, and so is never judged in relation to an abstract ideal and found lacking. Hence, “Adam’s appetite for earthly things was evil only in relation to our intellect, but not in relation to God’s” (Ep21).

Spinoza’s views on sin and evil deeply disturbed Blijenbergh and he countered this explanation with a further objection: if “there are no errors, there are no acts of knavery,” and if humanity really is without blame, then perhaps this means that “killing is as pleasing to God as giving charity” and “stealing as good as being just?” (Ep22). In addition to this question, Spinoza’s explanations trigger at least two further problems for his correspondent. First, if transgressions are not punished, then what could motivate virtuous actions? Second, if God is the cause behind every action, then how is it that God is not the cause of evil? Blijenbergh cannot grasp the idea that an ethical life does not require the existence of a transcendent authority who judges, rewards, and punishes human beings. For, if that were so, Blijenbergh worries, what could motivate anyone to do the right thing? He asks Spinoza, “What reason do I have for not eagerly committing all sorts of knavery (provided I can escape the judge). Why not enrich myself through abominable means?” (Ep22). For him, an immanent existence would entail an amoral world of sensual excess and thievery.

Spinoza’s response to these questions underlines his argument that virtue cannot be simply read off from the character of specific acts: wielding a knife, fornicating, stealing, giving alms. Virtue is not only a matter of what one does but more crucially concerns who one is, as his retort to Blijenbergh makes clear: “As for myself, I abstain from those things [acts of knavery], or try to, because they are explicitly contrary to my singular nature, and make me wander from the knowledge and love of God” (Ep21). For Spinoza, virtue is its own reward, not something we do in order to avoid punishment or gain favor. Indeed, Spinoza says that if a liar or a cheat finds that he can live a more powerful life through granting free rein to his vices then he would be foolish not to do so. But, to Spinoza, the very idea involves a contradiction: “if anyone sees that he can live better on the gallows than at his table, he would act very foolishly if he did not go hang himself” (Ep23). For such a perverse nature, Spinoza concludes, knavery would be virtue! In short then, Spinoza’s answer to the question: “Why be virtuous?” concerns the very essence and perfection of our being. We are most perfect, and real, when we express our essence and act from a clear knowledge of God and self because it is this knowledge that is “the principal thing that makes us men” (Ep23).

This distinction between act, on the one hand, and perfection or privation, on the other, leads to Blijenbergh’s second problem: if God is the cause of all actions, then he must be the cause of evil. In response to the provocative question about whether killing is pleasing to God, Spinoza patiently attempts to explain, again, that God is without passions or affects, which are inadequate and confused ideas, experienced only by finite beings. Using Nero’s matricide to illustrate his point, Spinoza describes it as an act that involves both a virtue (or perfection) and a vice. Insofar as the motion of Nero’s arm, thrusting up and down, expresses a power of the body, it expresses a perfection of nature; but insofar as Nero’s capacity to move his arm up and down was motivated by the desire to kill his mother it expresses a vice. Some may find that Spinoza’s description of Nero’s act in terms of being “ungrateful, without compassion, and disobedient” understates his crime but Spinoza’s point is that none of these attitudinal states expresses essence; rather, they signal Nero’s lack or privation of being. So, God cannot be the cause of Nero’s privation (which is conceivable by the human intellect only) but is the cause of Nero’s actions (Ep23). A similar argument is restated in the same letter, where Spinoza writes: “But if the question is ‘Whether the two acts [stealing versus being just], insofar as they are something real, and caused by God, are not equally perfect?’ then I say that, if we consider the acts alone, and in such a way, it may be that both are equally perfect” (Ep23). But the crucial point, the point that Blijenbergh never accepts, is that the possible equal perfection of the acts certainly does not mean that the just person and the thief are equally perfect. Although all that exists follows from God’s eternal laws, and depends upon God, this does not render all things equally excellent, either in degree or in essence. This is poetically expressed by Spinoza’s assertion that although “a mouse depends on God as much as an angel does, and sadness as much as joy, a mouse cannot on that account be a kind of angel, nor sadness a kind of joy” (Ep23).

Though the term “body” (corpus) is commonly used in the early modern period to refer both to material substance as such and to particular material objects, such as tables or golf balls, Spinoza generally reserves the term to refer to modes of Extended substance, that is, particular and determinate ways that extended substance can exist or particular and determinate forms extended substance can take. For example, in his definition of body in the Ethics, Spinoza writes: “by body I understand a mode that in a certain and determinate way expresses God’s essence insofar as he is considered an extended thing” (E2def1). Of course, not all modes of extended substance are bodies. For example, motion and rest, though modes of extended substance, are not themselves bodies. Bodies correspond roughly to particular material objects – both tables and golf balls, but also molecules and galaxies, and even the physical universe as a whole.

Spinoza’s views on the nature of body are important, in part because he explicitly links the powers of the mind to the powers of the body. For example, in Part 2 of the Ethics he claims that “to determine what is the difference between the human mind and the other ones [i.e., nonhuman minds], and how it surpasses them, it is necessary for us … to know the nature of its object, that is, of the human body” (E2p13s). In other words, if we want to come to know how human minds differ from, and surpass in their abilities, the minds of nonhuman organisms, then we can do so by looking at how the human body – which includes the brain – differs from other bodies. This link between the powers of the mind and the body goes on to play a key role in understanding the nature of ethical perfection, for instance, how the mind becomes eternal (E5p29). As such, understanding body is important not just for understanding Spinoza’s views of the physical realm, but also for understanding key theses about human minds and their flourishing.

But what is a body for Spinoza? It is not that easy to tell. As expressions of God’s essence, bodies strive. That is, each body “insofar as it can by its own power, strives to persevere in its being” (E3p6). But bodies are not unique in this regard – all modes of substance, whether bodies or ideas or some modes of some other attribute, strive. Bodies do differ from ideas (and other non-bodily modes) in that the bodies alone are expressions of Extension in particular (E2p6). But Spinoza is not always clear what Extension itself is. For example, he doesn’t offer a definition of Extension in the Ethics, and in one of the last letters of his life (Ep83), written to Tschirnhaus in 1776, he admits both that he has not yet worked out his theory of extended substance, and that his concept of Extension differs in important ways from the Cartesian concept (of that which occupies space). Understanding Spinoza’s notion of body therefore requires a more piecemeal undertaking.

The most important text for this undertaking is the so-called “Physical Digression” in the second part of the Ethics. (Spinoza discusses the nature of body at great length in the early DPP, but this is a work devoted to expositing Descartes’s thought, so should not be treated as if it reflected Spinoza’s own thought on body.) By the time of the Physical Digression, Spinoza has made clear that the physical world is a plenum (E1p15s) – that is, it is completely saturated with bodies, with no empty space between them. In the Digression, he outlines some of the basic features of individual bodies, including the following: bodies have kinetic properties, chiefly motion and rest (E2a1), which is the basis of their identity (E2L1); they causally interact with each other on the basis of these properties (E2L3); all their changes are externally caused rather than self-caused (E2L3); they are governed by inertial laws (E2L3c); they can together compose larger bodies (E2L4); those larger bodies can persist (E2L7).

Nevertheless, some key questions surrounding the nature of body remain. Here is a small sample. First, are there atoms in Spinoza’s system, or is matter infinitely divisible? Spinoza mentions “simplest bodies” in the Digression (E2L7s), suggesting that there is a bottom floor of matter, which cannot be divided further. But it is unclear whether he is entitled to such a claim. After all, indivisible bodies, or atoms, have historically been often associated with an empty space (“atoms and the void”), and Spinoza is clear that he rejects the notion of empty space (E1p15s). Likewise, the indefinite divisibility of body plays a key role in the all-important Cartesian theory of vortices (which, among other things, is intended to explain the force of gravity), and there is no evidence that Spinoza rejects that theory. So, the issue of simplest bodies is of great importance to understanding Spinoza’s concept of body.

Second, how exactly do individual bodies come to compose a larger body and remain so composed? Spinoza answers that they come to compose a larger body, and persist as that body, when the individual bodies maintain a fixed ratio of motion to rest among themselves (E2d7). But it is not clear what exactly a ratio of motion to rest is. For example, is the ratio a ratio of the number of moving parts to the number of parts at rest? Or is it a ratio of the total amount of motion of the parts to the total amount of rest of the parts? If so, how are total amounts computed? Is it a function of size and speed, or something else? Or is the ratio a ratio of the average motion of the moving parts and the average rest of the resting parts? Even in one and the same body, each of these ratios can differ, and some, but not all, might remain the same over time. So, we need to know more about the relevant ratio to know when bodies persist. Spinoza, unfortunately, offers nothing explicit to answer which ratio, if any, is the relevant one.

Finally, to what extent can Spinoza’s theory of body provide insight into the specifics of his theory of mind? Though he tells his readers that the two realms are isomorphic (E2p7) and that understanding the body is the key to understanding the mind (E2p13s), it is not clear how productive the comparison is when it comes to specifics. For example, in order for facts about body to inform us about, for example, how people reason, how they form beliefs, how they resist temptation, how they form emotional bonds, and so on, Spinoza would need, at the very least, to identify the bodily counterparts for each of these phenomena. Perhaps this identification is possible – but one would be forgiven for not holding one’s breath.

By bondage or servitude (servitudo), Spinoza understands subjection to external causes that oppose our striving to exercise those capacities characteristic of our natures, such as the ability to reason. We may distinguish heuristically between two notions of servitude in Spinoza: ethical and political. Spinoza himself does not make this distinction and, properly speaking, political slavery is a species of ethical slavery. “Human bondage” or ethical slavery refers to a condition in which external causes (“passions” or “fortune”) contradict our striving to develop and exercise the powers of our minds and bodies. Political slavery is more specific. It refers to those social and political forces that compel us to serve the interests of another rather than our own. Throughout Spinoza’s corpus, we find discussions of the obstacles we encounter when striving to do what is most to our advantage. In the political writings, Spinoza points to how political rule can be so hostile to the interests and well-being of its subjects that they become its “slaves.” Whereas someone is enslaved in the ethical sense any time she is driven to act to her disadvantage, someone is enslaved in a political sense when she acts at the same time for the advantage of another.

In Part 4 of Spinoza’s Ethics, titled “Of Human Bondage or the Power of Affects,” Spinoza defines bondage as humanity’s “lack of power to moderate and restrain the affects.” Most interpreters concerned with bondage in Spinoza focus on how finite existence entails universal subjection to passions (LeBuffe Reference LeBuffe2010a; Lordon Reference Lordon2014). As finite beings, we are necessarily “part of nature” and experience changes caused by external causes, over which we typically have little control. James, thus, concludes that, for Spinoza, “slavery is an inevitable part of human existence” (Reference Spinoza, Akkerman, Steenbakkers and Moreau2020b, 139). We can never hope to be entirely free of passions, but it is important to keep in mind that not all passions “enslave” us (James Reference James2020b, 146).

For Spinoza, when we are not the adequate cause of changes in our power to think and act, we suffer “affects” which are passions (E3def3). The changes in our power can be for better or for worse; our power increases in the case of joyful passions and decreases in the case of sad ones. Whether a passion contributes to bondage depends on whether it moves us to our advantage or to our disadvantage: “the man who is subject to affects is under the control, not of himself, but of fortune, in whose power he so greatly is that often, though he sees the better for himself, he is forced to follow the worse” (E4pref). Servitude, or bondage to the passions, obtains only when (i) we are moved more by passions than by reason; and (ii) those passions compel us to think and act to our own detriment, forcing us to “follow the worse.”

Because “everyone is born ignorant of everything” (TTP16.7), all human beings are led more by passion than by reason for much of our lives. Moreover, no matter how much wisdom and virtue we enjoy as we mature, we still get sick, hungry, and tired. Arguably, no one avoids being occasionally or momentarily overwhelmed by grief, excitement, or fear. Nevertheless, even if we cannot hope to master all our passions, it by no means follows that our passions always master us. Without passions, we would not be able to move about, learn, and grow. Spinoza maintains that an infant does not freely desire milk. Nevertheless, it would be incorrect to think that a newborn is in bondage to her yearning for milk, bodily proximity, and playful interactions. Such passions do not arise from reason, but they serve rather than harm the nursling. So, even if an infant cannot be called free insofar as she desires milk, neither is she enslaved. Frequently, passions are our helpers, attracting us to what contributes to our perseverance.

Most generally, in Spinoza’s terminology, a person is “under the control of fortune” when she is unable to do what conduces to the preservation (and enhancement) of her mind and body. “Fortune” refers to circumstances over which we have limited control – such as bodily health, weather variability, political stability – to which we inevitably have affective responses. Either joyful or sad passions can bring us under the control of fortune. Even though joyful passions are defined by a passage to greater perfection (E3p11s), excessive joys can divert or harm our minds and bodies (E4p43–44). Bondage to fortune, slavery to passions, indicates a lack of self-control but not necessarily an external controlling power, like a tyrant. Women, for example, sometimes appear in Spinoza’s writing as forces of fortune that can enslave and destroy men (e.g., E4p44s). Ethical or moral slavery to an object of lust, however, indicates being controlled by passions rather than by a human oppressor.

Spinoza often represents ethical slavery as a misrecognition of one’s own good. For example, humans can fall under the control of superstition, which is animated and preserved by fear, especially fear of divine punishment. Superstition, according to Spinoza, “seems to maintain that the good is what brings sadness, and the evil, what brings joy” (E4app31). Since sadness indicates a loss of power, superstition drives us to pursue what will in fact harm us under the guise of the good. This harm is reinforced when what might bring joy and nourish our strength of mind is avoided or shunned. Superstition is encouraged by the fear and anxiety that bad luck typically provokes, which can be exploited by people with malicious intentions (TTPpref). As a universal psychological propensity – “all men by nature are subject to superstition” (TTPpref7) – it is best understood in terms of “human bondage,” or ethical servitude.

The distinctive feature of what we could call “political slavery” is that an individual or a multitude is in bondage to another agent, which may be a person, institution, or government. Classical republicanism refers to rule as “arbitrary” when it does not consult, disregards, or crushes the interests and well-being of its subjects. To be “enslaved” to “arbitrary rule” is to be at the mercy of an alien, capricious, or hostile will. James argues that Spinoza draws on this tradition to represent political slavery as a form of rule that is antagonistic to reason and to popular welfare (Reference Spinoza, Akkerman, Steenbakkers and Moreau2020b).

In his TTP, Spinoza invokes the classical distinction between a son, a subject, and a slave. A son or a subject ought to be commanded in ways that serve their own interests, contribute to the development of their physical and intellectual capacities, and enable them progressively to “freely do what is best” for themselves and others (E2p49s). The commands issued to a slave, in contrast, “are concerned only with the advantage of the person issuing the command” (TTP16.33). Spinoza uses this understanding of slavery to point to deficient and pernicious forms of political rule.

Being constrained by laws or commands is compatible with political liberty if obedience to those laws or commands serves the one constrained. Here Spinoza’s TTP aligns with Aristotle’s Politics, which characterizes rulers as despotic when they act for their own good, at the expense of those they rule. This distinction becomes an important feature of the republican tradition, encapsulated in the Ciceronian motto, which Spinoza repeats (TTP16.33; TP3.14; TP7.5): the people’s welfare is the highest law (Cicero, On the Laws).

Spinoza aligns political slavery with passive obedience, sluggishness of spirit, and suppressed vitality. Forms of political rule can be so harsh that subjects’ lives become saturated with “unwilling” compliance and despair (Steinberg Reference Steinberg2018a, chap. 4). They become “useless” to themselves, unable to pursue what is to their advantage (TTP16.33):

Politically enslaved people “care only to avoid death” and “are forced to belong to the victor” (TP5.6). If conformity with the law or sovereign decrees contradict people’s most fundamental interest, which is to cultivate “the true virtue and life of the mind,” “we say that [they] are slaves” (TP5.5–6). Thus, in order to be considered free rather than enslaved, a commonwealth must be organized to protect and promote intellectual as well as physical life.

While most interpretations of bondage, even when driven by political concerns, have focused on Spinoza’s “anthropology of the passions” (Lordon Reference Lordon2014), scholars have also explored how social and political institutions encourage or interfere with human striving for liberty, intellectual power, and flourishing (Steinberg Reference Steinberg2018a). Spinoza’s notion of freedom has long captured the attention of scholars, but a great deal remains to be explored in Spinoza’s analysis of servitude.

Johannes Bouwmeester was one of Spinoza’s closest friends and associates. Though he played a vital part in disseminating Spinoza’s philosophy, Bouwmeester’s preferred position was in the background.

Bouwmeester was born in Amsterdam on November 4, 1634 (not 1630, as is commonly assumed; see Mertens Reference Mertens2011, 122–23). He obtained his doctorate in Leiden with a medical dissertation on May 27, 1658 and moved back to Amsterdam, where he set up as a medical practitioner. Bouwmeester died in Amsterdam in October 1680.

Lodewijk Meyer and Bouwmeester appear to have been inseparable. Their friendship likely started when they were medical students in Leiden in the 1650s. They became part of the Amsterdam circle of friends and admirers of Spinoza sometime between 1658 and 1661. The anonymously published treatise Philosophia S. Scripturae interpres (1666), usually ascribed to Lodewijk Meyer, may well have been the result of a collaboration with Bouwmeester. In 1669, they were both among the founders of Nil volentibus arduum, a literary society that remained active for decades. Both contributed several chapters to its collective project, Onderwys in de tooneel-poëzy (1669–71). In 1672, Nil published Bouwmeester’s Dutch translation (done from Latin) of Ibn Tufayl’s twelfth-century philosophical novel Hayy ibn Yaqzan. After 1677 Bouwmeester and Meyer joined the board of the Amsterdam municipal theatre. They were involved in the pamphlet war known as the Amsterdam physicians’ quarrel of 1677.

Though Spinoza did not publish anything until 1663, his fame as an original thinker (and notoriety as an atheist) already began to spread in the late 1650s. Bouwmeester and Meyer were among the friends who urged Spinoza to expand his partial outline of DPP and publish it with its supplement, CM. Meyer copy-edited the text and wrote a preface (see Ep12a and Ep15), Bouwmeester contributed a dedicatory Latin poem, Pieter Balling made a Dutch translation, and Jan Rieuwertsz published both versions.

In Spinoza scholarship, Bouwmeester is generally identified as the addressee of Ep28, written around June 12, 1665, which has come down to us only as a draft, without date or recipient’s name. Though later deemed unworthy of publication by the editorial team of the Opera posthuma (which included Meyer and Bouwmeester), the letter is of great historical importance: it informs us about Spinoza’s work in progress. Spinoza asks the unknown recipient if he would be willing to make a Dutch translation of Ethics Part 3. Ep28 is also remarkable because of its intimate tone; the addressee must have been one of Spinoza’s closest friends. Though Bouwmeester, who was a gifted Latinist, met all the requirements to be considered the recipient, we cannot be certain. The situation is different for Ep37, written by Spinoza on June 10, 1666, published posthumously as addressed to ‘J. B.’

The recent discovery of nine letters from Bouwmeester to J. G. Graevius, written between April 18 and August 25, 1673, reveal that Bouwmeester – offstage – continued to assist Spinoza (Gootjes Reference Gootjes2016). In this case he appears to have acted as a sort of impresario. The Utrecht Cartesians, with Graevius as their secretary, negotiated with Bouwmeester to invite Spinoza to Utrecht, then occupied by the French army. On August 7, at a moment when the English fleet threatened to attack The Hague while Spinoza was still in Utrecht, Bouwmeester wrote to Graevius that Spinoza’s work – the unfinished Ethics – was in danger. Fortunately, the attack did not take place after all. Why Spinoza went to Utrecht is still a mystery (Gootjes Reference Gootjes2020).

Spinoza died on February 21, 1677 in The Hague. A group of friends in Amsterdam took it upon themselves to publish the Ethics, as well as other works and letters they found in the writing box that Spinoza’s landlord had shipped to Jan Rieuwertsz. Meyer and Bouwmeester prepared the Latin Opera posthuma for the press; Jarig Jelles, Jan Rieuwertsz and Jan Hendriksz Glazemaker took care of its Dutch counterpart, De nagelate schriften.

Hugo Boxel was the author of Ep51, 53, and 55 to Spinoza, and the recipient of Ep52, 54, and 56. This correspondence took place from September to October/November 1674 and suggests the two had met before and conversed. It covers the unlikely topic of apparitions and ghosts and has often been regarded as one of the oddest episodes in Spinoza’s correspondence, although during the second half of the seventeenth century the belief in ghosts, witches, and magic was still widespread across Europe; the Dutch Republic was no exception.

The dates of Hugo Danielsz. Boxel’s life are uncertain: he is reported to have been born in Heusden, possibly in 1607, and he seems to have passed away in 1680. We do know for sure that he took his doctorate in philosophy in Leiden on July 14, 1626. Subsequently he appears to have studied law in Paris. Next, Boxel held a legal practice at the Court of Holland and simultaneously served as secretary of the city of Gorinchem (1634 to 1645 and 1655 to 1659), after which he acted as its pensionary from 1660 to 1672, when he was removed from office by William III. From 1654 to 1659 he was one of the ouderlingen (elders) of the local reformed community. He published two legal editions, one treatise by the Genoese lawyer Ettore Felici, another by the Leiden law professor Cornelis van Nieuwstadt.

Boxel’s correspondence with Spinoza allowed the latter to explore the philosophical issue of testimony, for Boxel argued that the great number of stories from antiquity involving ghosts rendered their non-existence highly unlikely. Spinoza countered by stating he knew of no credible author who had demonstrated their existence conclusively and by raising the question whether anybody actually knew what kinds of beings ghosts were. On the contrary, according to Spinoza, ghost stories illustrate, if anything, the extent to which people are prone to relate not what’s really the case, but rather how they would like the world to look. Boxel would not let go of his conviction and continued, in Ep53, to indicate a number of metaphysical arguments in favor of the existence of non-material beings. He invoked for instance the principle of plenitude, according to which God must have created such beings if only in order to fill the gap between himself and human beings, who are both spiritual and material. Boxel felt a universe filled with ghosts to be more beautiful than one without them, which left him with the question whether there were female ghosts. Next, he listed a number of credible authors reporting apparitions, including Suetonius, Wier, Lavater, Cardanus, and Melanchthon. Spinoza’s elaborate reply in Ep54 concentrates on Boxel’s notions of perfection and beauty, which to his mind were anthropomorphic. In his final letter, Boxel attempted to circumvent this claim, at which point Spinoza made an end to this exchange of letters by presenting his own conviction that we have a perfectly adequate idea of God. On his view, while it is impossible to have a perfect understanding of all of God’s attributes, some of them are fully intelligible.

Robert Boyle was perhaps the finest experimental natural philosopher of his age. He was active in the Republic of Letters, being one of the founding members of the Royal Society and a correspondent with scientific luminaries of his day. He was in broad strokes an adherent of what was then called the mechanical philosophy, which held that all qualities of natural things could be reduced to the properties of matter in motion. He was a reductionist about qualities, holding that “almost all sorts of qualities … may be produced … by such corporeal agents as do not appear either to work otherwise than by virtue of the motion, size, figure, and contrivance, of their own parts” (Boyle Reference Boyle1666, preface)

Boyle was also an experimentalist about scientific knowledge. Rather than begin with first indubitable principles which would then ground hypotheses about the nature of bodies, his aim was “to devise experiments, and to enrich the history of nature with observations faithfully made and delivered; that by these and the like contributions made by others, men may in time be furnished with a sufficient stock of experiments, to ground hypotheses and theories on” (Boyle Reference 581Boyle1773, 121). Here Boyle is following the Baconian inductive method – to which, it should be said, Spinoza pays at least lip service. He writes in TTP that “the method of interpreting nature consists above all in putting together a history of nature, from which, as from certain data, we infer the definition of natural things” (TTP7.7); and in Ep6 that he thinks a history (in Bacon’s sense) of fluids is “something all Philosophers ought greatly to desire, as being very necessary” (Ep6).

Boyle’s interaction with Spinoza was mediated by Henry Oldenburg. Oldenburg and Boyle had met while the former was serving as tutor to the latter’s nephew, Robert Jones. Oldenburg sent Spinoza a copy of one of Boyle’s works, Certain Physiological Essays (almost certainly the Latin version, Tentamina quaedam physiologica, since Spinoza could not read English) with a letter dated October 21, 1661. Spinoza read the book and responded with a letter of his own. The exchange comprises Ep6, 11, and 13. Ep6 and 13, from Spinoza to Oldenburg, are some of the longest in Spinoza’s oeuvre.

It is difficult to say with certainty whether Boyle influenced Spinoza, or vice versa. But it seems unlikely. In their mediated exchange, they largely just disagree. This disagreement stems, at least in part, from their wildly different conceptions of scientific method. Boyle, as we said above, was a more or less strict experimentalist, who sought to found theories about (to take the case in the correspondence) the nature of niter on experimental data. Spinoza, on the other hand, did not think that experience could reveal the natures of things; only the highest kind of cognition could do that (see TIE[29]). He writes that Boyle’s experiments are no better than other (it should be said, much worse) experiments that Spinoza mentions, “from which, however, this [the hypothesis concerning the nature of niter] is not proven” (Ep13). Little about Spinoza’s views seems to have changed after the exchange, and Boyle, for his part, continued his experimental investigations more or less untroubled.