Descartes's greatest glory was to be the first to articulate, and systematically to defend, the new scientific ideal of explanation in terms of lawfulness. For the realm of matter, lawful connections replaced anthropomorphic volitions as the model of rational explanation. (That he retained anthropomorphic volitional explanation for the realm of mind is understandable: you cannot expect a man to jump wholly out of his skin. It would prove easier, after Newton, to make the extension to mind.) Descartes's use of explanation in terms of lawfulness, inspired by Galileo's beginnings in this enterprise, was vindicated by Newton's subsequent achievement. Replacement of anthropomorphic agency, by causal mechanism, as the explanatory model, was undoubtedly the most profound of the many effects of the new science on our culture.

On the very first page of Spinoza's Ethics we find the perplexing definition of ‘attribute’: ‘By an attribute I mean what the understanding perceives in regard to a substance as constituting its essence’. Each attribute of a substance by itself thus constitutes the essence of a substance; if there are many attributes of the same substance, it does not take all of them together to constitute its essence. Spinoza, as we all know, in fact held that there is only one substance, God, but there are infinitely many attributes, of which only two, Thought and Extension, are accessible to the human mind. Each attribute, we further learn, has to be conceived on its own account (I, prop. 10); being conceived on its own account is, however, a distinguishing mark of the one substance, so how is it that the many attributes, which Spinoza says are really distinct, are not so many distinct substances, so many gods?

That is the ontological side of the puzzle. Now for the logical or grammatical side — about which writers on Spinoza have, I think, said a great deal less, though it has been much discussed as regards less deviant theology than Spinoza's. Each attribute is clearly meant to be a concrete, active, individual entity; yet the attributes are designated by abstract nouns — ‘Thought’ and ‘Extension’. Now can we make sense of such a sentence as ‘God is Thought’ or ‘God is Extension’, as opposed to ‘God thinks’ or ‘God is extended’? What does it mean to predicate an abstract noun of a concrete individual? And if this ‘is’ here is not a bare copula of predication but an identity sign, then how can we avoid passing from ‘God is Thought’ and ‘God is Extension’ to ‘Thought is Extension’? Spinoza would deny the conclusion, and it is quite essential to his system to do so. For if Thought just is Extension, identically so, then any mode of the attribute Thought is a mode of the attribute Extension and vice versa. But for Spinoza, the last is diametrically opposite to the truth: no mode is a mode of more than one attribute, and indeed no causal relations link modes of different attributes — a causal linkage is always confined to one attribute.

I propose, in this paper, to offer a simple, even perhaps a simplified, version of Spinoza's metaphysical views, and to show how these views sometimes affected his epistemological views.

When they did affect his epistemological views the effect was always a bad one, since Spinoza's metaphysical system is quite unworkable. It is helpful, and sometimes even inspiring, but it is wrong. In the end, with the epistemology as with the metaphysics, nothing of substance will be salvageable, but Spinoza's new and even radical perspective is worth observing for its own sake, and there are points of detail along the way, ranging from inspired falsehoods to cloudy truths, that still deserve the effort to untangle them.

In order to understand the thoughts of Leibniz it is important to stop putting Leibniz into the convenient pigeon-hole of rationalist, and stop thinking of him merely as the metaphysician and constructor of systems so vividly ridiculed by Voltaire in Candide. Most important of all, one should not attempt to see Leibniz's philosophy as a completely articulated and integrated whole or as built on three or five metaphysical and logical principles. It is better to remember that Leibniz was a very prolific writer, who was interested in the most varied aspects of philosophy, logic, mathematics, natural science, jurisprudence, history and philology: a man who was constantly trying to work out a large number of heterogeneous theories and thoughts. The collected editions of his writings make up more than twenty thick volumes, and these hardly exhaust his manuscripts. Yet this was a man who published only one book in his lifetime.

That the legacy of Berkeley's philosophy has been a largely sceptical one is perhaps rather surprising. For he himself took it as one of his objectives to undermine scepticism. He roundly denied that there were ‘any principles more opposite to Scepticism than those we have laid down’ (PHK, 40). Yet Hume was to write of Berkeley that ‘most of the writings of that very ingenious author form the best lessons of scepticism, Bayle not excepted’. And it has become something of a commonplace to say that Berkeley's philosophy is sceptical in direction, if not in intention. He is represented as a half-hearted sceptic, applying radical empiricist principles in his treatment of matter but baulking at their implications when he came to consider spirits. Hume is credited with being the more thoroughgoing of the two. Berkeley had denied the substantiality of extended things. Hume felt obliged, by parity of reasoning, to deny the substantiality of the self. On his account of the mind there is ‘properly no simplicity in it at one time, nor identity in different’ (THN, 1 iv 6). It is commonly supposed that Berkeley, in maintaining the quite contrary view that we know ourselves to be simple, undivided beings (PHK, 27), showed a lack of rigour or consistency.

Ontology was never Hume's main interest, but he certainly had opinions as to what there is, and he often expressed these in his philosophical works. Indeed it seems clear that Hume changed his ontological views while writing the Treatise, and that not just one but two different ontologies are to be found there. The ontology of Parts I, II, and III of Book I is more or less Lockean. There are minds and their operations and qualities. There are physical entities, bodily actions and qualities if not bodies over and above these. And there are further entities, called ideas by Locke and perceptions by Hume, that represent things other than themselves, both physical and mental, while existing in and being dependent upon minds. In Part IV of Book I, however, and especially in Sections 2 and 6, a new ontology appears, one that differs not only from the doctrine of the earlier sections of the Treatise but also from any that previous philosophers had held. According to this new ontology, there are only perceptions: all other sorts of things are absorbed by or reduced to these, or else simply eliminated. Berkeley had indeed assimilated bodies and the properties of bodies to perceptions, but he had kept minds as a distinct category of entity. Hume went the whole way, making everything perceptions. We might characterise this new ontology as trans-Berkeleyan, or call it, on account of its similarity to later doctrines so named, phenomenalism or neutral monism.

Hume's explicit pronouncements about truth are few and unenlightening. In a well-known passage near the beginning of Book III of the Treatise (III i 1; p. 458 in Selby-Bigge's edition) he writes that ‘Reason is the discovery of truth or falsehood. Truth or falsehood consists in an agreement or disagreement either to the real relations of ideas, or to real existence and matter of fact.’ Hume's main concern in this passage, however, is not with the concept of truth, but with his thesis that moral distinctions are not derived from reason: he introduces his reference to truth only with a view to showing that our ‘passions, volitions and actions … being original facts and realities, complete in themselves,’ are not susceptible of the agreement and disagreement spoken of, and therefore cannot be said to be true or false, in conformity with or contrary to reason. The account of truth given here is not elaborated, and perhaps not even thought to need elaboration. Similarly with another passage a few pages earlier in which Hume says that ‘Truth is of two kinds, consisting either in the discovery of the proportions of ideas, considered as such, or in the conformity of our ideas of objects to their real existence’ (T, ii iii 10; 448 SB). Here again his interest is not in truth itself but in ‘curiosity, or the love of truth,’ the passion which, Hume says, ‘was the first source of all our inquiries’ (ibid.). Hume seems to take it for granted that nothing more needs to be said about what it is to discover ‘the proportions of ideas, considered as such,’ or about the circumstances in which we can speak of there being ‘conformity’ or the lack of it between our ideas of objects and their real existence. So far as he is concerned the central point to grasp is the distinction between propositions which have to do with relations of ideas and those which express, or purport to express, matters of fact. Once this distinction is clear, the nature of truth is supposed to be plain.

Rousseau seldom gets a mention as a philosopher in the conventional histories; if he appears at all it is in connection with that strange and rather suspect discipline ‘political philosophy’. Even then there is a tendency to look upon him as an unsystematic thinker, as a ‘philosophy’ rather than as a genuine philosopher. His ideas are held to be interesting, but the connections between them are thought to be emotional rather than logical. Again, Émile is read by students of education, but not by those studying philosophy. This is both because the ‘philosophy of education’ is thought not to be of great importance and again because of Rousseau's lack of logical rigour. Now it is true that Rousseau himself was an emotional figure, and from reading his Confessions it is easy to get the idea that there is no point in looking for interesting philosophical points in his works.

Kant was an idealist. His idealism was in some ways, it is true, less extreme than that of Berkeley. He distinguished his own by calling it ‘transcendental’. It is less extreme than Berkeley's in two ways. First, Kant does not assert that everything which exists is essentially mental, as Berkeley does. Second, those things which he does hold to be essentially mental, he holds to be so in a weaker fashion. Nevertheless he was an idealist; he held that neither intuition nor thought could concern any object that was not essentially related to our minds. Since intuition and thought together provide knowledge, and since we can have no knowledge except through them, it follows that every object of which we have knowledge is essentially within our minds. Moreover, there is at least one respect in which his idealism is more extreme than that of Berkeley. He held that the objects of intuition were essentially within our minds, whereas Berkeley held only that they were essentially within some mind.

‘The Principle of Sufficient Reason in all its forms is the sole principle and the sole support of all necessity. For necessity has no other true and distinct meaning than that of the infallibility of the consequence when the reason is posited. Accordingly every necessity is conditioned; absolute, i.e. unconditioned, necessity therefore is a contradicto in adjecto. For to be necessary can never mean anything but to result from a given reason.’ These words are taken from the beginning of section 49 of Schopenhauer's The Fourfold Root of the Principle of Sufficient Reason. They express sentiments with which I am to some extent in agreement, and it therefore seemed to me worth while to explore in some kind of detail Schopenhauer's treatment of the issues. It might, however, be asked why the view expressed by Schopenhauer should be of philosophical interest, what, if anything, turns on the rejection of the notion of absolute necessity. To this I can reply by saying only that apart from the intrinsic interest of the notion of necessity itself, an issue on which a philosopher ought to make himself clear, Schopenhauer himself points to some of the consequences of his doctrine - the impossiblity, for example, of an absolutely necessary being, and the similar impossibility of ontological or cosmological arguments

‘Force and Understanding’ is the title, or part of the title, of the third section of Hegel's Phänomenologie des Geistes, his ‘phenomenology of spirit’. That was his first book; it was published in 1807 as Volume One of his System of Science. A second volume, he announced, would contain ‘the system of Logic as speculative philosophy, and of the other two parts of philosophy, the sciences of Nature and Spirit’. But no such volume appeared: although in 1812 his Science of Logic was published as ‘the first sequel to the Phenomenology of Spirit in an expanded arrangement of the system’, Hegel added to the 1831 edition a note explaining that since then he had brought out his Encyclopaedia of the Philosophical Sciences ‘in place of the projected second part’.

The concept of freedom is one which Hegel thought of very great importance; indeed, he believed that it is the central concept in human history. ‘Mind is free’, he wrote, ‘and to actualise this, its essence – to achieve this excellence – is the endeavour of the worldmind in world-history’ (VG, p. 73). Those who already have an interest in Hegel will doubtless be interested in his views on a topic which he thought so important; on the other hand, the many philosophers who are either indifferent to or hostile to Hegel may point out that it does not follow that, because the subject of freedom interested Hegel, his views about this subject are of general interest. It will be the aim of this paper to show that they are of general interest; in the meantime, it may be recalled that Isaiah Berlin has argued (Four Essays on Liberty, Oxford, 1969, p. 144) that Hegel's concept of freedom is one of a type, called by him the concept of positive freedom, which is ‘at the heart of many of the nationalist, communist, authoritarian and totalitarian creeds of our day’. It will surely be worth while to see to what extent this is true of Hegel, and to what extent Hegel's views about freedom are true.

The principle of utility is Bentham's basic test for morals and legislation. But there is room for doubting what that principle is supposed to say. I shall argue that one important element of modern utilitarian doctrines Cannot be found in Bentham's.

Some aspects of his views will not be questioned here. He holds, for example, that acts should be appraised by their consequences alone. The effects that count are ‘pleasures’ and ‘pains’, that is, the effects upon human happiness, interest or welfare.

It would be an exaggeration to say that the Victorian age in England was philosophically barren; but it would not be a great exaggeration. By this somewhat uncomplimentary opening, I do not mean to imply that Victorian England contained no competent philosophers at all. Indeed, if one considers thinkers of the second and lower ranks only, their literary productivity was probably greater than those of any previous period in English, or even British, history, even if in sheer numbers they can hardly compete with the prolific hordes of our own century. It is at the very highest level of philosophical greatness and originality that one finds the Victorian age wanting. The great period of British philosophy, which runs roughly from the 1630s to the 1770s, contains at least three thinkers who cannot be matched in the succeeding 140 years, Hobbes, Locke and Hume.