2.1. Three questions

I will now begin the preliminary task of distinguishing different questions about the phenomenology of believing.

Most philosophers of mind agree that sensory states, such as perceptions, imaginations, and bodily sensations, have some phenomenology. For instance, the visual experience of a red apple on the table has some (visual) phenomenology. Q1 asks whether not only sensory states but also beliefs have some phenomenology.Footnote ⁴ It asks whether not only the visual experience of a red apple on the table but also the belief about a red apple on the table has some phenomenology.Footnote ⁵

It is one thing to say that beliefs have some phenomenology, but it is another to say that the mental state of believing is defined by its phenomenology. To say that believing is defined by its phenomenology is to be committed to a strong claim that a mental state is a belief rather than something else (e.g., a desire, an imagining, etc.) because of its phenomenology, or that the phenomenology makes it the case that the state is a belief rather than something else.

You can coherently give a “Yes” answer to Q1 and a “No” answer to Q2; for example, you might think that the belief that there is a red apple on the table has some phenomenology, but that it is not the case that this is a belief rather than something else because of its phenomenology. Perhaps it is a belief rather than something else because of its functional role. In contrast, if your answer to Q2 is “Yes,” then your answer to Q1 must also be “Yes”; if you think that the belief that there is a red apple on the table is a belief rather than something else because of its phenomenology, then you cannot deny that the belief has some phenomenology without being incoherent.

Q3 is the main question in this article. To say that beliefs have cognitive phenomenology is to be committed to the view that beliefs have a non-sensory and distinctively cognitive kind of phenomenology. The phenomenology is “non-sensory” in the sense that it is different in kind from sensory phenomenology. The phenomenology is “distinctively cognitive” in the sense that it is the kind of phenomenology that is peculiar to cognitive mental states, such as the state of believing.

The cognitive phenomenology of believing can take different forms. Following Bayne and Montague (Reference Bayne, Montague, Bayne and Montague2011), we can distinguish the attitudinal cognitive phenomenology of believing from the content cognitive phenomenology of believing. As we will see in Section 3.1, my focus will be on the former rather than the latter.

The attitudinal cognitive phenomenology of believing is associated with the attitude of believing rather than the believed content. For example, the attitudinal cognitive phenomenology of the belief that there is a red apple on the table is associated with the attitude of believing rather than the believed content “there is a red apple on the table.” If the belief that there is a red apple on the table has attitudinal cognitive phenomenology, then we can expect there to be a non-sensory phenomenal difference between this belief and another state with the same content, such as the imagining that there is a red apple on the table (assuming that believing and imagining do not share the same attitudinal cognitive phenomenology). In contrast, the content cognitive phenomenology of believing is associated with the believed content rather than the attitude of believing. For example, the content cognitive phenomenology of the belief that there is a red apple on the table is associated with the believed content “there is a red apple on the table” rather than the attitude of believing. If the belief that there is a red apple on the table has content cognitive phenomenology, then we can expect there to be a non-sensory phenomenal difference between this belief and another belief with different content, such as the belief that there is a green apple on the table.

Note that even when you say that beliefs have cognitive phenomenology, you might not be committed to the stronger view that cognitive phenomenology is the only kind of phenomenology beliefs have, or that beliefs do not have sensory phenomenology. It is a coherent possibility that beliefs have both sensory and cognitive phenomenologies. This will be crucial later on; I will argue that Hume is committed to the cognitive phenomenology of believing (CPI), which is perfectly compatible with the idea that Hume is also committed to the sensory phenomenology of believing.

You can coherently give a “Yes” answer to Q1 and a “No” answer to Q3; for example, you might think that the belief that there is a red apple on the table has some phenomenology, but that its phenomenology is totally sensory. The phenomenology of believing that there is a red apple on the table is the same in kind as the phenomenology of seeing a red apple on the table. There is some phenomenal difference between the belief about a red apple on the table and the visual experience of it, but the difference is in degree, not in kind; for example, the latter is more vivid than the former. In contrast, if your answer to Q3 is “Yes,” then your answer to Q1 must also be “Yes”; if you think that the belief that a red apple is on the table has cognitive phenomenology, then you cannot deny that this belief has some phenomenology without being incoherent.

You can coherently give a “Yes” answer to Q2 and a “No” answer to Q3; for example, you might think that the belief that a red apple is on the table is a belief because of its phenomenology, but that the relevant phenomenology is totally sensory. Perhaps it is a belief because of its distinctively low degree of sensory vividness. Again, you can coherently give a “Yes” answer to Q3 and a “No” answer to Q2; for example, you might think that the belief that a red apple is on the table has cognitive phenomenology, but it is not the case that this is a belief rather than something else because of its cognitive phenomenology (or any other phenomenology it might have). Perhaps it is a belief rather than something else because of its functional role.

In summary, with respect to Q1, Q2, and Q3, there are five possible views in total, which are summarized below.

CPI says that Hume is committed to the cognitive phenomenology of believing; in other words, Hume’s answer to Q3 is “Yes.” This implies that Hume’s position is either View 1 or View 3. CPI is neutral on Q2; Hume’s answer to Q2 might be “Yes” (in which case his position is View 1) or it might be “No” (in which case his position is View 3). In contrast, CPI is not neutral on Q1; both View 1 and View 3 are committed to a “Yes” answer to Q1.

2.2. Hume on Q1 and Q2

Let us now closely examine Hume’s answers to Q1, Q2, and Q3. It is likely that Hume’s answer to Q1 is “Yes”; beliefs do have phenomenology (in a broad sense of the term “phenomenology”; see footnotes 3 and 8). This means that we can rule out View 5 as Hume’s position. For instance, Hume repeatedly describes beliefs by using terms that are naturally and plausibly taken to be phenomenal terms; for example, Hume talks of “additional force and vivacity” (T 1.3.7.5, SBN 96) and “a certain feeling or sentiment” (T App.2, SBN 624).Footnote ⁶ Hume also draws an analogy between the feeling of believing with “the feeling of cold or passion of anger” (E 5.12, SBN 48).Footnote ⁷ Although, as we will see in Section 4.4, there are some debates among commentators (e.g., Everson Reference Everson1988; Loeb Reference Loeb2001, Reference Loeb2002; Marušić Reference Marušić2010) concerning the significance of phenomenology for Hume’s account of believing (which is about Q2), it is relatively uncontroversial that beliefs have some phenomenology (which is about Q1) in Hume’s theory of mind.Footnote ⁸

Hume’s answer to Q2 is more elusive than his answer to Q1. It is relatively uncontroversial that Hume’s official answer to Q2 is “Yes.” Both in the Treatise and the Enquiry, Hume’s definition of belief seems to be a phenomenal one: in the Treatise he says that belief is “nothing but a peculiar feeling, different from the simple conception” (T App.3, SBN 624); in the Enquiry he says that “the whole nature of belief” consists in “a feeling or sentiment, different from the loose reveries of the fancy” (E 5.11, SBN 48). But there is a controversy as to whether Hume’s official phenomenal definition of believing should be taken at face value. Several commentators have pointed out that Hume’s description of beliefs is not phenomenal, but rather dispositional or causal (see footnote 24). Some argue that, in addition to the official commitment, Hume has an unofficial commitment that believing is defined by its dispositional profile (Loeb Reference Loeb2001, Reference Loeb2002) or its functional role (Everson Reference Everson1988). Marušić (Reference Marušić2010), in contrast, insists that Hume’s account of believing is exhausted by the official phenomenal definition; there is no need to attribute an unofficial definition to him.

Q2 is not the main question of this article; I will not discuss whether Hume defines the mental state of believing by its phenomenology. This article defends CPI, which is neutral on Q2.

2.3. Hume on Q3

Q3 is the main focus of this article. According to CPI, which I defend, Hume’s answer to Q3 is “Yes”: beliefs do have cognitive phenomenology. This means that we can rule out View 2 and View 4 as Hume’s position. Hume’s position is thus either View 1 or View 3.

In the contemporary literature on cognitive phenomenology, Hume is typically regarded as a philosopher with a “No” answer to Q3. The phenomenal difference between the belief about a red apple on the table and the visual experience of it is a difference of degree, not a difference in kind; the latter has a higher degree of “force” and “vivacity” than the former (e.g., Prinz Reference Prinz, Bayne and Montague2011; Siewart Reference Siewart, Bayne and Montague2011; Smithies Reference Smithies2013; Spener Reference Spener, Bayne and Montague2011). Hume is committed to empiricist psychology according to which all mental operations are grounded in sensory experience. This empiricist commitment seems to imply that all phenomenal characters, including the phenomenology of believing, are reduced into some sensory phenomenal characters. According to empiricist psychology, the belief about a red apple on the table is grounded in the visual experience of a red apple on the table (or, perhaps, the conjunction of the visual experience of a red apple, the visual experience of a table, etc.). This seems to imply that the phenomenology of the belief about a red apple on the table is the same in kind as the phenomenology of the visual experience of a red apple on the table. The upshot is that, given Hume’s commitment to empiricist psychology, his answer to Q3 must be “No.”

I have two responses to this reasoning: the rebuttal response (which challenges the conclusion of the reasoning) and the undercutting response (which challenges the process of the reasoning). The rebuttal response is developed in the main part of this article (Sections 3 and 4) in which I argue that textual evidence does not support the conclusion of this reasoning.

The undercutting response is that Humean empiricist psychology does not rule out cognitive phenomenology. In other words, Humean empiricist psychology and cognitive phenomenology are perfectly consistent with each other. A crucial part of Humean empiricism is the so-called Copy Principle, which Hume takes to be a more sophisticated expression of the Lockean denial of innate ideas (E 2.9n1.1, SBN 22).

The Copy Principle does not rule out cognitive phenomenology. It says that, for all X, if you have a (simple) idea of X, there must be a prior (simple) impression of X. But it does not say anything about the phenomenology of the idea of X and the impression of X; in particular, it does not say that the (believed) idea of X and the impression of X share the same kind of phenomenology. It is perfectly consistent with the Copy Principle to say that the (believed) idea of X and the impression of X are phenomenally different in kind.

However, one might not be convinced. A possible objection is that the Copy Principle is not consistent with the claim that the idea of X and the impression of X are phenomenally different in kind, given an additional assumption that an impression and an idea cannot share the same content, X, when they are phenomenally different in kind. According to the Copy Principle, for all X, when you have an idea of X, there must be a prior impression of the same content, X. Given the additional assumption, it is impossible for an idea and an impression to have the same content, X, when they are phenomenally different in kind. Hence, the idea of X and the impression of X cannot be phenomenally different in kind.

In response, I agree that the Copy Principle together with the additional assumption rule out cognitive phenomenology, but I do not know why the additional assumption should be attributed to Hume. In fact, the additional assumption seems to contradict some of Hume’s remarks on beliefs (see CONTENT-NEUTRALITY in Section 3.3).

Another objection is that my interpretation of the Copy Principle is too weak. The Copy Principle does not merely say that an impression of X precedes an idea of X, it also says that the latter is “deriv’d from” the former such that the latter is a “faint” copy of the former. Moreover, the idea of “faint” copying seems to imply that the phenomenal difference between the idea of X and the impression of X is a difference of degree, in particular the degree of “force” and “vivacity.”

In response, it is one thing to say that the idea of X and the impression of X differ in their degree of “force” and “vivacity,” but it is another thing to say that this is the only phenomenal difference between them. The former view is safely attributable to Hume,Footnote ⁹ but the latter is not. In fact, Hume eventually rejects the view that the only phenomenal difference between the (believed) idea of X and the impression of X is the difference in the degree of “force” and “vivacity” (see Section 3.2).

3.1. Cognitive phenomenal interpretation

According to CPI, Hume is committed to the cognitive phenomenology of believing. More precisely, he is committed to the attitudinal cognitive phenomenology of believing. Hume is committed to the idea that believing is characterized by its distinctive “manner” of conception; in other words, there is a distinctive “manner” in which believed ideas are conceived. Hume later (i.e., in the Appendix and the Enquiry) identifies the distinctive “manner” of believing with the distinctive “feeling” of believing. My claim is that CPI provides us with the best explanation of Hume’s remarks on the distinctive “manner” or “feeling” of believing. In short, the distinctive “manner” or “feeling” of believing consists in the attitudinal cognitive phenomenology of believing.

Note that I do not claim that Hume is committed to the content cognitive phenomenology of believing. Hume would acknowledge a phenomenal difference between the belief that a red apple is on the table and the belief that a green apple is on the table, but the phenomenal difference between them might be totally sensory (e.g., phenomenal redness/greenness). Hereafter, the phrase “cognitive phenomenology” means “attitudinal cognitive phenomenology.”

3.2. From early view to late view

A complication is that Hume’s discussions of belief go through some important changes. In particular, there are crucial differences between (i) Hume’s remarks on beliefs in Section 1.3.7 of the Treatise (his “early” remarks) and (ii) his remarks in the AppendixFootnote ¹⁰ and in the Enquiry (his “late” remarks).Footnote ¹¹ As we will see, Hume’s early remarks suggest that believing is characterized by a certain degree of sensory phenomenology (“force” and “vivacity”). This amounts to a “No” answer to Q3. But early discussions are not fully satisfactory for Hume, which is why he adds further comments on the nature of believing in the Appendix. Hume’s late remarks suggest that believing is characterized by a non-sensory phenomenology, which is different in kind from “force” and “vivacity.”Footnote ¹² This amounts to a “Yes” answer to Q3. In short, Hume’s early answer (in Section 1.3.7 of the Treatise) to Q3 is “No,” while his late answer (in the Appendix and in the Enquiry) is “Yes.”

Hume’s Early View: In Section 1.3.7 of the Treatise, Hume first establishes that believing is characterized by a distinctive “manner” of conception rather than by a distinctive idea. Hume considers the scenario in which two people, say A and B, disagree on a particular issue. For example, A believes that Caesar died in his bed, whereas B does not. Although B does not believe that Caesar died in his bed, B perfectly understands what A means by “Caesar died in his bed,” and clearly imaginesFootnote ¹³ that Caesar died in his bed. Hume rejects the idea that what distinguishes A (who believes that Caesar died in his bed) from B (who imagines that Caesar died in his bed without believing it) is some distinctive idea, such as the idea of “existence,” that A conceives (but B does not). Hume insists that B “form[s] all the same ideas, which [A] forms” and B’s “imagination is endow’d with the same powers as [A’s], nor is it possible for [A] to conceive any idea, which [B] cannot conceive; or conjoin any, which [B] cannot conjoin” (T 1.3.7.3, SBN 95). What distinguishes A from B is rather the distinctive “manner” in which A conceives of the ideas; A and B conceive of the same set of ideas (the idea of Caesar, the idea of death, the idea of bed, etc.) but they do so in different “manners.”

Hume goes on to argue that the distinctive “manner” of believing is a distinctive degree of “force” and “vivacity”: “[s]o that as belief does nothing but vary the manner, in which we conceive any object, it can only bestow on our ideas an additional force and vivacity” (T 1.3.7.5, SBN 96). A’s belief that Caesar died in his bed has a stronger degree of force and vivacity than B’s imagining that Caesar died in his bed. Hume’s main reason for this view is that the degree of “force” and “vivacity” is the only variable that can differentiate A’s belief from B’s imagining, which follows from his two premises; first, A’s belief and B’s imagining involve the same set of ideas and, second, the difference between A’s belief and B’s imagining consists either in different ideas or in different degrees of “force” and “vivacity.”

Thus, according to Hume’s early view, believing is characterized by its distinctive “manner,” which is identified by the distinctive degree of “force” and “vivacity.” This view can be taken as a “No” answer to Q3, assuming that “force” and “vivacity” in Section 1.3.7 of the Treatise refer to some sensory phenomenology.Footnote ¹⁴ “Force” and “vivacity” are the terms Hume uses to distinguish impressions from ideas in Section 1.1.1 of the Treatise. As several commentators have noted (e.g., Bennett Reference Bennett2001; Owen Reference Owen1999), there is a considerable similarity between Hume’s remark on the belief/imagining distinction in Section 1.3.7 of the Treatise and his remark on the impression/idea distinction in Section 1.1.1 of the Treatise. It is plausible that in the context of the impression/idea distinction, “force” and “vivacity” refer to some sensory quality. Using the same terms in the context of the belief/imagining distinction, Hume seems to suggest that the distinctive manner of believing has something to do with sensory phenomenology.

Hume’s Late View: Hume is not fully satisfied with his early view, which is why he revisits the issue of believing in the Appendix. In the Appendix, Hume still maintains the idea that believing is characterized by a distinctive “manner” of conception rather than a distinctive idea, but he now rejects the idea that the distinctive manner of believing is nothing but a distinctive degree of “force” and “vivacity.” He is now skeptical about his earlier assumption in Section 1.3.7.5 of the Treatise that the degree of “force” and “vivacity” is the only variable that can differentiate A’s belief that Caesar died in his bed from B’s imagining it. Hume in the Appendix calls this assumption in Treatise 1.3.7.5 an “error” (T App.22, SBN 636) and argues: “I believe there are other differences among ideas, which cannot properly be comprehended under these terms. Had I said, that two ideas of the same object can only be different by their different feeling, I shou’d have been nearer the truth” (T App.22, SBN 636). It is not the case that A’s belief that Caesar died in his bed and B’s imagining it can differ only in the degree of “force” and “vivacity.” There are “other differences” between them, which “cannot properly be comprehended under” the terms like “force” and “vivacity.” The differences are about “their different feeling.”

Thus, in the Appendix, Hume rejects his early claim that the distinctive manner of believing consists in a distinctive degree of “force” and “vivacity.” According to his late view, the distinctive “manner” of believing consists in a distinctive “feeling” of believing, which “cannot properly be comprehended under” the terms such as “force” or “vivacity.”Footnote ¹⁵ According to CPI, the distinctive “feeling” is the cognitive phenomenology of believing. Next, we will look deeper into the textual evidence for CPI.

3.3. Explaining textual evidence

I will now defend CPI with an inference to the best explanation of textual evidence; CPI provides us with the best explanation of Hume’s late remarks of believing in the Appendix and in the Enquiry.

The first explanandum about Hume’s late remarks, which I call “FEELING,” is that beliefs have a peculiar “feeling.” For instance, A feels something when A believes that Caesar died in his bed.

The second explanandum, “ASYMMETRY,” is that beliefs have a peculiar feeling that imaginings do not have. For instance, A’s belief that Caesar died in his bed has the peculiar feeling of believing, but B’s imagining that Caesar died in his bed does not have the same feeling. Hume’s commitment to FEELING and ASYMMETRY is evident in his claim that believing “is something felt by the mind, which distinguishes the ideas of the judgment from the fictions of the imagination” (T 1.3.7.7, SBN 629).Footnote ¹⁶

The third explanandum, “UNIQUENESS,” is related to, but stronger than, ASYMMETRY. The peculiar feeling of believing uniquely characterizes the mental state of believing in the sense that all and only beliefs have this feeling. If a mental state is a belief, then it has the peculiar feeling of believing. If a mental state is not a belief, then it does not have the peculiar feeling of believing. Hume’s commitment to UNIQUENESS is evident in his official definition of believing in terms of its peculiar feeling: “belief is nothing but a peculiar feeling” (T App.3, SBN 624).Footnote ¹⁷

The fourth explanandum, “CONTENT-NEUTRALITY,” is that the peculiar feeling of believing does not modify ideas in the sense that it is possible that two people, A and B, conceive of the same idea of X, but only A feels the peculiar feeling of believing; B does not feel it. For example, both A, who believes that Caesar died in his bed, and B, who imagines that Caesar died in his bed, conceive of the same ideas (i.e., the idea of Caesar, the idea of death, the idea of bed, etc.), but only A feels the peculiar feeling of believing; B does not feel it. Hume’s commitment to CONTENT-NEUTRALITY is evident in his rejection of the idea that believing consists in “new idea, such as that of reality or existence, which we join to the simple conception of an object” (T App.2, SBN 623).Footnote ¹⁸

The fifth explanandum, “NON-FORCE/VIVACITY,” is that the peculiar feeling of believing cannot be captured by “force,” “vivacity,” or related terms. The peculiar feeling of believing cannot be identified with a strong degree of “force” and “vivacity.” Hume’s commitment to NON-FORCE/VIVACITY is evident in his claim that the distinctive feeling of believing “cannot properly be comprehended under” the terms such as “force” or “vivacity” (T App.22, SBN 636). Similar claims are repeated in the Appendix and in the Enquiry, where Hume tries to describe the feeling of believing with a variety of terms, including “force,” “vivacity,” “liveliness,” etc., but no term satisfies him. Hume ends up saying that the best thing he can do is to just call it the feeling of “belief”: “[w]e may make use of words that express something near it. But its true and proper name is belief, which is a term that everyone sufficiently understands in common life” (T 1.3.7.7, SBN 629).Footnote ¹⁹

The sixth, and related explanandum, “ELUSIVENESS,” is that the peculiar feeling of believing is elusive. A striking feature of Hume’s late discussions of believing in the Appendix and in the Enquiry is his reluctance to say what the distinctive “manner” or “feeling” actually is. He talks about what it is not (e.g., it is not a strong degree of “force” and “vivacity” [T App.22, SBN 636]), and compares it with other feelings (e.g., it is compared with impressions [T App.3, SBN 624-5]), but admits “that ‘tis impossible to explain perfectly this feeling or manner of conception” (T 1.3.7.7, SBN 629).Footnote ²⁰ Because of the elusive nature of believing, Hume finds “a considerable difficulty” in defining beliefs, is “at a loss for terms” to describe beliefs, and admits that the nature of believing is “one of the greatest mysteries of philosophy” (T 1.3.7.7, SBN 628).

CPI can explain these explananda. According to CPI, A’s belief that Caesar died in his bed has cognitive phenomenology, which A consciously feels (FEELING). The phenomenology is non-sensory, which is why it cannot be fully captured by “force,” “vivacity,” or other sensory terms (NON-FORCE/VIVACITY). It is the cognitive phenomenology of believing, which A’s belief has but B’s imagining does not (ASYMMETRY). More generally, the (attitudinal) cognitive phenomenology of believing uniquely characterizes the attitude of believing (UNIQUENESS). (Attitudinal) cognitive phenomenology does not modify content (CONTENT-NEUTRALITY); for example, A, who believes that Caesar died in his bed, and B, who imagines that Caesar died in his bed, conceive of the same ideas, but only A experiences the (attitudinal) cognitive phenomenology of believing.

CPI also explains ELUSIVENESS because cognitive phenomenology is expected to be more elusive than sensory phenomenology. For instance, Prinz talks about “the elusiveness of purely cognitive qualities” (Prinz Reference Prinz, Bayne and Montague2011, 193), and Horgan argues that “sensory phenomenology is more strikingly vivid than cognitive phenomenology” (Horgan Reference Horgan, Bayne and Montague2011, 77).

4.1. Three alternatives

The aim of Section 3.3 was to establish that CPI gives us a plausible explanation of relevant textual evidence. Section 4 aims to examine alternative readings and show that none of them are more plausible than CPI and hence that CPI is the best explanation of relevant textual evidence.

I divide alternative interpretations into two groups. First, there are alternatives according to which the distinctive “manner” of believing consists in some phenomenology other than cognitive phenomenology. Second, there are alternatives according to which the distinctive “manner” of believing consists in some non-phenomenal property.

In the first group, I discuss two notable interpretations: the one according to which the distinctive “manner” of believing consists in some sensory phenomenology (the “sensory phenomenal interpretation” [SPI], see Section 4.2), and the one according to which it consists in some agential phenomenology (the “agential phenomenal interpretation” [API], see Section 4.3). In the second group, I will focus on the interpretation according to which the distinctive “manner” of believing consists in some causal or dispositional property (the “non-phenomenal interpretation” [NPI], see Section 4.4).

4.2. Sensory phenomenal interpretation

Let us begin with SPI. As I mentioned above, Hume argues that the “manner” or “feeling” of believing “cannot properly be comprehended under” the terms “force” or “vivacity” (NON-FORCE/VIVACITY). However, one might think that it would be too hasty to conclude from this that the “feeling” of believing is non-sensory. Even if the feeling of believing is different from “force” and “vivacity,” and even if it is granted that “force” and “vivacity” refer to a sensory phenomenology, it does not follow that the “feeling” of believing is non-sensory. Arguably “force” and “vivacity” would not be the only kind of sensory phenomenology; there are other kinds of sensory phenomenology, such as color phenomenology or sound phenomenology. NON-FORCE/VIVACITY is consistent with the interpretation that the “feeling” of believing consists in some sensory phenomenology that is different from “force” and “vivacity,” which is what SPI suggests.

SPI is certainly consistent with NON-FORCE/VIVACITY, but it fails to explain some other explananda. For example, SPI is unlikely to explain CONTENT-NEUTRALITY. In the Humean psychological framework, sensory phenomenology typically modifies content. For example, color phenomenology modifies content; it is not possible for two people, A and B, to conceive of the same ideas but experience different color phenomenologies; for example, A experiences a reddish phenomenology while B experiences a bluish phenomenology. In other words, if A and B experience different color phenomenologies, then they conceive of different ideas; for example, A entertains the idea of redness and B entertains the idea of blueness.Footnote ²¹

Sensory phenomenology typically modifies content. The only exception Hume recognizes is “force” and “vivacity”: “[w]hen you wou’d any way vary the idea of a particular object, you can only increase or diminish its force and vivacity. If you make any other change on it, it represents a different object or impression. […] A particular shade of any color may acquire a new degree of liveliness or brightness without any other variation. But when you produce any other variation, ‘tis no longer the same shade or color” (T 1.3.7.5, SBN 96). Thus, there is at least a kind of sensory phenomenology that satisfies CONTENT-NEUTRALITY; that is, “force” and “vivacity.” However, the “feeling” of believing cannot be identified with “force” and “vivacity” for an obvious reason, namely NON-FORCE/VIVACITY.

Another problem of SPI is that it does not account for ELUSIVENESS. Sensory phenomenology, such as color phenomenology, is typically “more strikingly vivid than cognitive phenomenology” (Horgan Reference Horgan, Bayne and Montague2011, 77) and thus perhaps there is nothing particularly elusive about it.

However, there is some room for a debate on ELUSIVENESS. The defenders of SPI might argue that the elusive nature of believing is just an instance of a general fact about phenomenology of any kind; any sort of phenomenology, sensory or cognitive, is elusive in the sense that it is difficult to provide a satisfactory verbal description of it. For example, it is difficult to describe what it is like to see maple leaves on a sunny day in autumn, especially when you try to describe it for a color-blind person. The “feeling” of believing is difficult to describe for the same reason that the visual experience of maple leaves on a sunny day in autumn is difficult to describe.

According to the present proposal, the “feeling” of believing is elusive not because it involves a particularly elusive kind of phenomenology but rather because it is difficult to give a satisfactory verbal description of phenomenology of any kind. Interestingly, this account of ELUSIVENESS is consistent with Hume’s remark in the Enquiry where he compares the difficulty of describing the “feeling” of believing with the difficulty of describing other kinds of phenomenology: “[w]ere we to attempt a definition of this sentiment [of believing], we should, perhaps, find it a very difficult, if not an impossible task; in the same manner as if we should endeavor to define the feeling of cold or passion of anger, to a creature who never had any experience of these sentiments” (E 5.12, SBN 48).

However, this account of ELUSIVENESS is not fully satisfactory. I do admit that the elusiveness of believing is partially due to the general difficulty of verbally describing phenomenology. But it cannot be the whole story. In addition to the general difficulty of verbally describing phenomenology, there is a particular kind of elusiveness Hume finds in the “feeling” of believing. After all, if the problem of elusiveness had been nothing but the general problem of verbally describing phenomenology, then “force” and “vivacity” would have been elusive as well. As a matter of fact, however, Hume does not think that “force” and “vivacity” are elusive in the way that the “feeling” of believing is. Hume struggles to say what the “feeling” of believing actually is in the Treatise (1.3.7.7) and in the Enquiry (5.12), and confesses that the nature of the “feeling” is “one of the greatest mysteries of philosophy” (T 1.3.7.7, SBN 628). In contrast, Hume does not say that the nature of “force” and “vivacity” is particularly mysterious. Hume talks about “force” and “vivacity” as if they are clear and obvious in the Treatise (1.1.1), and he continues to do so in the Enquiry (2).

Thus, the textual evidence suggests that the “feeling” of believing is particularly elusive, and that this elusiveness is something more than the general difficulty of verbally describing phenomenology. SPI fails explain the particularly elusive nature of the “feeling” of believing (while CPI does explain it).

4.3. Agential phenomenal interpretation

According to API, the “feeling” of believing has something to do with agential phenomenology, where “agential phenomenology” refers to the subjective experience of a bodily movement or a mental event as an action.Footnote ²²

API is motivated by the following observation: in describing the “feeling” of believing, Hume says that beliefs are “firm,” “solid,” or “steady” in the context of comparing beliefs with imaginings. Beliefs are “firm,” “solid,” or “steady” in comparison to imaginings. This observation suggests the following interpretation: Hume’s terms such as “firm,” “solid,” and “steady” describe a salient phenomenal difference between beliefs and imaginings, namely, the difference with regard to agential phenomenology. Beliefs are “firm,” “steady,” and “solid” in comparison to imaginings in the sense that imagining is an act and experienced as such, while believing is not. In fact, Hume repeatedly points out that imagining is an act that is under our voluntary control: “[w]e may mingle and unite, and separate, and confound, and vary our ideas in a hundred different ways; but ‘till there appears some principle, which fixes one of these different situations, we have in reality no opinion” (T 1.3.7.4, SBN 96).

API is certainly an attractive interpretation,Footnote ²³ but it is not fully satisfactory. A serious problem of API is that it does not explain ASYMMETRY. ASYMMETRY says that beliefs have something (i.e., a peculiar “feeling”) that imaginings do not, while API says that imaginings have something (i.e., agential phenomenology) that beliefs do not.

There are some possible available responses by the defenders of API. For instance, they might argue that Hume misdescribes the difference between believing and imagining. As a matter of fact, he refers to the difference in terms of agential phenomenology when he uses the terms “firm,” “steady,” and “solid.” For some reason, however, he mistakenly takes the difference to be due to something beliefs have but imaginings do not. Alternatively, the defenders of API might argue that, in addition to the phenomenology of agency, Hume is committed to the phenomenology of the lack of agency. The terms “firm,” “steady,” and “solid” refer to the phenomenology of the lack of agency, which beliefs have but imaginings do not. I do not rule out these responses, but there is some doubt as to whether API, even supplemented with these assumptions, is as plausible as CPI. Accounting for ASYMMETRY, API needs some extra assumptions such as the assumption that Hume was wrong about what he was talking about (the first response), or that Hume was committed to some additional phenomenology (the second response). In contrast, CPI does not need these extra assumptions and thus gives a more parsimonious explanation of ASYMMETRY.

Even if API can somehow account for ASYMMETRY, it fails to explain UNIQUENESS. After all, the lack of agential phenomenology does not uniquely characterize the mental state of believing; there are many other mental states that lack agential phenomenology. It is certainly true that the lack of agential phenomenology distinguishes the belief about a red apple on the from the imagining about it (because only the latter has agential phenomenology). But it does not distinguish the belief about a red apple on the table from the desire about it or the visual experience of it (because all lack agential phenomenology). Does Hume mistakenly think that the lack of agential phenomenology uniquely characterizes the mental state of believing? Attributing such an implausible commitment to Hume is rather uncharitable.

4.4. Non-phenomenal interpretation

According to NPI, the distinctive “manner” of believing is not phenomenal; rather, it consists in some dispositional or causal property. To say that beliefs are conceived in a distinctive “manner” is to say that beliefs have some distinctive dispositional or causal property.

NPI is motivated by the observation that some of Hume’s remarks on belief do not sit well with his official phenomenal definition of belief. He does say, officially and explicitly, many things that support the phenomenal reading of some kind (CPI, SPI, or API), but he also makes other comments that do not sit well with the phenomenal reading, which can be taken as evidence that Hume has an unofficial and implicit commitment that beliefs are characterized by their causal or dispositional properties.

For example, several commentators point out that some of the terms Hume uses to describe believing, such as “solidity” or “steadiness” (T 1.3.7.7, SBN 629: see also E 5.12, SBN 49), do not look like phenomenal terms; they look more like causal or dispositional terms.Footnote ²⁴ This observation aligns with the fact that Hume tries to explain these terms with reference to causal consequences. Loeb (Reference Loeb2001, Reference Loeb2002) points out that the terms that Hume uses to describe believing can be divided into two groups or clusters: the vivacity cluster and the steadiness cluster. The vivacity cluster includes “vivacity,” “vividness,” “intensity,” and “liveliness,” and the steadiness cluster includes “firmness,” “solidity,” and “steadiness.” Loeb argues that the steadiness cluster terms are more fundamental than the vivacity cluster terms in Hume’s theory of belief, and that the steadiness cluster terms refer to a dispositional property rather than a phenomenal property.Footnote ²⁵

In response, however, it is certainly true that some of Hume’s terms, the ones in the steadiness cluster in particular, do not appear to be sensory phenomenal terms (which raises a problem for SPI), but I insist that they can be understood as cognitive phenomenal terms. (Or, more precisely, these terms can be understood as a failed attempt to refer to cognitive phenomenology. After all, Hume himself admits that these terms are not perfectly satisfactory in Section 1.3.7.7 of the Treatise and in Section 5.12 of the Enquiry.)

Both the defenders of NPI and I agree that Hume’s terms—the ones in the steadiness cluster in particular—are not sensory phenomenal terms. Our disagreement is that the defenders of NPI take them to be non-phenomenal, causal, or dispositional terms, while I take them to be non-sensory phenomenal terms. There is at least prima facie advantage for my reading, which is more coherent with the textual evidence than NPI. For Hume, the vivacity cluster terms and the steadiness cluster terms are interchangeable, and the terms in both clusters describe the feeling of believing: “this different feeling I endeavor to explain by calling it a superior force, or vivacity, or solidity, or firmness, or steadiness” (T 1.3.7.7, SBN 629). This clearly suggests that Hume’s terms, including the vivacity cluster terms and the steadiness cluster terms, refer to a phenomenal property.Footnote ²⁶

Does NPI really explain the explananda about Hume’s remarks on believing? At a first glance, NPI does not even explain FEELING; after all, dispositional or causal properties cannot be felt, at least in the Humean psychological framework. But defenders of NPI can respond to this worry, for example, by distinguishing Hume’s official and explicit claims from his unofficial and implicit claims. FEELING is about Hume’s official and explicit commitments while NPI aims to capture his unofficial and implicit commitments. Alternatively, defenders of NPI can respond to this worry by distinguishing the dispositional property of believing from its manifestations (Loeb Reference Loeb2001, Reference Loeb2002); although the dispositional property of believing itself cannot be felt, its manifestations include some conscious episodes that can be felt.

These responses are certainly available, but note that, with these responses, NPI might not be a real alternative to CPI. In other words, NPI might be compatible with CPI. When it comes to the first response (of distinguishing official and explicit commitments from unofficial and implicit commitments), NPI is perfectly compatible with the idea that Hume’s official and explicit position is that beliefs have some phenomenology, possibly cognitive phenomenology. When it comes to the second response (of distinguishing the dispositional property of believing from its manifestation), NPI is perfectly compatible with the idea that beliefs, when manifested, have some phenomenology, possibly cognitive phenomenology.

There is another reason why NPI might not be a real alternative to API. NPI is often presented as an answer to Q2: the proposal is that Hume defines beliefs in terms of some causal or dispositional property rather than some phenomenal property. For example, Loeb’s claim is that “[w]e must, systematically, identify beliefs with steady dispositions” (Loeb Reference Loeb2001, 289). This amounts to a “No” answer to Q2. As I have previously explained in Section 2.1, a “No” answer to Q2 is perfectly compatible with a “Yes” answer to Q3; one can coherently argue that beliefs are defined by some causal or dispositional property rather than by some phenomenal property (NPI) and still claim that beliefs have some phenomenal property that is non-sensory and distinctively cognitive (CPI).