1 “It seems to me like straw.” These are the words Aquinas is said to have used when describing his life's work in comparison with a “vision” (possibly a stroke) he experienced towards the end of his life. See Weisheipl'és, JamesFriar Thomas D'Aquino: His Life, Thought and Works (Washington, DC: Catholic University of America Press, 1983)Google Scholar. The idea that one might use these words while peering through a cerebroscope comes from the cover of Francis Spar-shott's delightful book, Looking for Philosophy (Montreal: McGill-Queen's University Press, 1972).Google Scholar

2 Hume, David, in his A Treatise of Human Nature (edited by Selby-Bigge, L. A. [Oxford: Oxford University Press, 1888])Google Scholar denies that introspection gives us an experience of the self on several grounds. First, he denies that experience yields any idea of the self “for from what impression cou'd this idea be deriv'd?” (ibid., p. 251). No impression is constant and invariable enough to give us the idea of a self persisting through change (ibid.). Impressions “are distinguishable, and separable from each other, and may be separately consider'd, and may exist separately, and have no need of anything to support their existence” (p. 252). Finally, there is no experience of a self because “[f]or my part, when I enter most intimately into what I call myself, I always stumble on some particular perception or other, of heat or cold, light or shade, love or hatred, pain or pleasure. I never catch myself at any time without perception, and never can observe any thing but the perception” (p. 252).

3 Roderick Chisholm makes this point against Hume in “On the Observability of the Self,” reprinted in Self-Knowledge, edited by Cassam, Quassim (Oxford: Oxford University Press, 1994), pp. 94–108, esp. p. 95.Google Scholar

4 See Aquinas, Thomas, Summa Theologiae, I, q. 86, 1 (London: Blackfriars & Eyre and Spottiswood, 1968), Vol. 12Google Scholar. The analogy between indirect knowledge of singulars through the phantasms and perceiving objects in a mirror is given at Quaestiones disputatae de veritate in Opera Omnia, XXII, I (Rome: Leonine Commission, 1975); hereafter De Veritate, I, q. 2, 6: “The likeness (similitudo) which is in sense abstracted from the thing as from an object of knowledge (cognoscibili) and, therefore, through that likeness the same thing itself is known directly. The likeness which is in the intellect is not abstracted from a phantasm as from an object of knowledge but as from a medium of knowledge through the mode in which our sense receives the likeness of a thing which is in a mirror; as long as the intellect is directed to it not as to a certain thing but as to a likeness of a thing.”

5 For a discussion of displaced perception as a model for introspection see Dretske's, Fred “Introspection,” in Proceedings of the Aristotelian Society, 94 (1994): 263–78.CrossRefGoogle Scholar

6 Michael Marmura has identified Avicenna's opponents as the Islamic speculative theologians (mutakallimuri). See Marmura's, Michael “Avicenna's ‘Flying Man’ in Context,” Monist, 69 (1986): 383–95, esp. pp. 383–84.CrossRefGoogle Scholar

7 Avicenna, , De Anima, edited by Van Riet, S. (Leiden: E. J. Brill, 1972)Google Scholar, la pars, c. 1, 11. 49–60: “Suppose that one of us must think as if he were suddenly createdcomplete but with his sight obscured so that he could not see outside. And suppose that he were created as if he were moved in the air or the void in such a way that he was not touched by the thickness of the air that he would be able to sense it and as if his limbs were separated so that they did not strike either him or each other. Thence he should see if he affirms being of his essence. He will not hesitate to affirm himself to exist. He will not however affirm things exterior to his members nor the hidden things of his interiors nor his soul nor his brain nor anything else extrinsic. But he will affirm himself to exist though he will not affirm the length or the width or the thickness of himself. If however in that period of time it were possible for him to imagine a hand or another member, that would not be imagined to be part of him nor necessary to his essence.”

8 Aquinas, Summa Theologiae, I, q. 75, 1.

9 De Veritate, q. 10, 8, d. 9.

10 De Veritate, q. 10, 8, d. 15.

11 De Veritate, q. 10, 8, d. 11.

12 The dependence of the soul upon the body is a central theme in Aquinas's treatise on human nature. See Summa Theologiae, I, q. 76, a. 5.

13 At De Veritate, q. 10, 8, Aquinas distinguished two types of individual knowledge of the soul: habitual, which the intellect has prior to the abstraction of species, and actual, which the intellect has only subsequent to the abstraction of species. The distinction is described thus: “Our intellect can understand nothing actually before it abstracts from phantasms; neither can it have a habitual notion of things other than itself, which are not in itself before the aforementioned abstraction in that species of other things which are not innate in it. But its own essence is innate to it so that it does not necessarily have to acquire it from phantasms; just as the essence of matter is not acquired from a natural agent but only its form, which thus is compared to natural matter as intelligible form is to sensible matter, as the Commentator says. And therefore before the mind abstracts from phantasms, it has a habitual notion of itself, by which it is able to perceive that it exists.”

14 Aquinas, Summa Theologiae, I, q. 87, a. 4.

15 Aquinas standardly uses the perceptual verb percipere to describe the soul's intellectual awareness of itself except in an unpublished determinatio attributed to Aquinas: Quaestio Disputata Utrum Anima Coniuncta Cognoscat Seipsamper Essentiam, transcribed in Kennedy's, L. A. “The Soul's Knowledge of Itself,” in Vivarium, 15, 1 (1977): 31–45CrossRefGoogle Scholar, where the verb cognoscere is used. I doubt that this terminological difference is significant. Both verbs imply a kind of knowledge weaker than that which relies on proof such as scire.

16 This is stated in the reply to the second objection at Summa Theologiae, I, q. 87, a. 3, and refers back to q. 86, a. 2, where Aquinas explains how a finite mind can nonetheless cognize a potentially infinite series of acts.

17 Aquinas, Summa Theologiae, I, q. 87, a. 3: “Therefore, that which is first known by the human intellect is an object of this kind (the nature of a material thing); and secondarily is known the very act by which the object is known; and through the act is known the intellect itself, the perfection of which is the act itself of understanding.”

18 De Veritate, q. 10, 8, reply to d. 9.

19 In the following footnotes, I make use of the standard abbreviations of editions of Descartes works: AT for Oeuvres de Descartes, Vols. 1–12, edited by Adam, Charles and Tannery, Paul (Paris: Leopold Cerf, 1897–1913)Google Scholar; CSM for The Philosophical Writings of Descartes, Vols. 1–2, translated by Cottingham, John, Stoothoff, Robert, and Murdoch, Dugald (New York: Cambridge University Press, 1985Google Scholar [Vol. 1], 1984 [Vol. 2], and Vol. 3, translated by John Cottingham, Robert Stoothoff, Dugald Murdoch, and Anthony Kenny (New York: Cambridge University Press, 1991).

The most familiar statement of the cogito is from the Second Meditation {AT, Vol. 7, p. 25; CSM, Vol. 2, p. 17): “But there is a deceiver of supreme power and cunning who is deliberately and constantly deceiving me. In that case I too undoubtedly exist, if he is deceiving me; and let him deceive me as much as he can, he will never bring it about that I am nothing so long as I think I am something. So after considering everything very thoroughly, I must finally conclude that this proposition, I am, I exist, is necessarily true whenever it is put forward by me or conceived in my mind.”

20 Aquinas, Summa Theologiae, I, q. 87, a. 1, and.De Veritate, q. 10, 8.

21 SeeDescartes'Optices IV-VI,AT Vol.6, pp. 109–148; CSM, Vol. l, pp. 164–75.

22 Descartes, Reply to Second Objection, Third Set of Replies (AT, Vol. 7, pp. 175–76; CSM, Vol. 2, p. 124): “It is certain that a thought cannot exist without a thing that is thinking; and in general no act or accident can exist without a substance for it to belong to. But we do not come to know a substance immediately, through being aware of the substance itself; we come to know it through its being the subject of certain acts.”

See also AT, Vol. 8A, p. 25; CSM, Vol. 1, p. 210, where Descartes argues that a substance can only be known through its acts because this is the only way a substance affects us. One perhaps question-begging reason offered as to why we can be certain there is a substance wherever there is an act is that “nothingness possesses no attributes.”

23 Second Replies, in AT, Vol. 7, p. 140; CSM, Vol. 2, p. 100: “When someone says ‘I am thinking, therefore I am, or I exist,’ he does not deduce existence from thought by means of a syllogism, but recognizes it as something self-evident by a simple intuition of the mind. This is clear from the fact that if he were deducing it by means of a syllogism, he would have to have had previous knowledge of the major premiss ‘Everything which thinks is, or exists’; yet in fact he learns it from experiencing in his own case that it is impossible that he should think without existing. It is in the nature of our mind to construct general propositions on the basis of our knowledge of particular ones.”

24 Second Meditation, in AT, Vol. 7, p. 33; CSM, Vol. 2, p. 22: “For if I judge that the wax exists from the fact that I see it, clearly this same fact entails much more evidently that I myself also exist.”

25 Aquinas, Summa Theologiae, I, q. 87, a. 3: “The act of understanding is not the act and perfection of the material nature understood, just as if by one act the nature of a material thing and the act of understanding could be understood. Whence there is one act by which the intellect understands stone, and another by which it understands that it understands stone, and so on.”

26 The example of reviewing is Ryle's, Gilbert in “Self-Knowledge,” reprinted in Self-Knowledge, edited by Cassam, Quassim (Oxford: Oxford University Press, 1994), pp. 19–42, esp. p. 39.Google Scholar

27 Interestingly, the view that the self is constantly aware of itself also seems to have been shared by Avicenna. See Marmura, “Avicenna's ‘Flying Man,’” p. 391.

28 In saying “I am, therefore I exist” is the first and most certain proposition, Descartes writes, at Principles, I. 10, that he does “not deny that one must first know what thought, existence and certainty are, and that it is impossible that that which thinks should not exist” (AT, Vol. 8A, p. 8; CSM, Vol. 1, p. 196). In order to avoid an obviously vicious circle, Descartes must intend that the last claim be read as a conceptual truth. Hence, Descartes goes on to say, “But because these are very simple notions, and ones which provide us with no knowledge of anything that exists, I did not think they needed to be listed” (ibid.). If I am right, the truth of “if x thinks, x exists” is analytic for Descartes, which is why he does not think he needs an additional argument to infer his existence from his awareness of his thinking.

29 See AT, Vol. 7, pp. 139–40; CSM, Vol. 2, p. 100.

30 See Descartes's Discourse on Method, Part 4, AT, Vol. 6, p. 32; CSM, Vol. 1, p. 127.

31 This is Elizabeth Anscombe's objection in “The First Person,” in Mind and Language, edited by Guttenplan, S. (Oxford: Oxford University Press, 1975), pp. 45–65, esp. p. 58.Google Scholar

32 See also Peter Markie's discussion of Descartes's problems with the elusive self in “The Cogito and Its Importance,” in The Cambridge Companion to Descartes, edited by Cottingham, John (New York: Cambridge University Press, 1992), pp. 140–73CrossRefGoogle Scholar, esp. pp. 163–65. Markie points out that the evidence suggests that Descartes relationally individuates himself even though this is an untenable position. There is an assumption behind these sorts of objections that self-individuation is a necessary part of individual self-knowledge, an assumption I question was shared by either Descartes or his predecessors.

33 Aquinas, Summa Theologiae, I, q. 107, a. 1.

34 De Veritate, q. 10, 9.

35 Ibid., Reply.

36 A discussion of the analogy between habitual knowledge of the soul and grammar is to be found in the unpublished Determinatio, Quaestio Disputata Utrum Anima Coniuncta Cognoscat Seipsam per Essentiam, where Aquinas writes: “[b]ut about an habitual cognition, by which someone is able to know promptly and easily, I say that the soul knows itself through its own essence, just as if a human being has the habit of grammar then grammar perfects the intellect of that human inasmuch as it is concerned with speaking grammatically, namely syntactically [congrue] and properly, because a habit is a principle or quality difficult to move by which someone easily operates and enters into an act of cognition, and so because he has a habit of grammar presently [presencialiter] he speaks grammatically. So I say about an habitual cognition. Because the soul is present to its very self, that presence alone suffices for its knowing itself through an habitual cognition. How does the presence of the soul suffice? Because acts flow from the soul through which it is discovered in the cognition of the power and from the cognition of the power it is discovered in the cognition of the essence. But in speaking of the cognition of actual existence thus it knows itself through its own act.”

37 That we are aware of exercising our capacity for self-knowledge as well as being aware of the mind's acts is clear from Aquinas's texts. For example, at De Veritate, q. 10, 9, Reply, he writes: “[w]ith reference to habitual knowledge, habits of the mind are said to be known through themselves. For the cause of habitual knowledge is that by which someone is rendered capable of going forth into (exire) the act of knowing the thing which is said to be known habitually. From the very fact that habits are in the mind through their essence, the mind can enter upon actual perception of the existence of habits within it, insofar as through the habits which it has it can enter upon acts in which the habits are actually perceived.”

38 I am grateful to Peter King, Christopher Martin, and Calvin Normore for discussion and suggestions.