¹ René Descartes, The Meditations Concerning First Philosophy in Philosophical Essays. Translated by Laurence J. Lafleur (Indianapolis: Bobbs-Merrill, 1964), 59–143, 80.

² Ibid., 75.

³ Ibid., 77.

⁴ Frankfurt rightly argues that Descartes' doubt of mathematical judgment is general and not specific to these kinds of judgments:

Harry G. Frankfurt, Demons, Dreamers and Madmen (New York: The Bobbs-Merrill Company, 1970), 78.

It is, however, important to note that although Descartes points out a psychological bias, he turns it into philosophical doubt by a logical move: from the recognition of actual misjudgment to the possibility of permanent misjudgment.

⁵ Op. cit. note 1, 79.

⁶ Ibid., 79–80.

⁷ Bair argues that Descartes failed to control his own self-deception, and wrongly considered his feigned denials to be genuine in order to conclude that he can be a thinking being without a body. She goes on to claim that his objectors, Mersenne, Arnould and Gassendi, pointed out his mistake

Annette C. Bair, ‘The vital but dangerous art of ignoring: selective attention and self-deception’, in Self and Deception, edited by Roger T. Ames and Wimal Dissanayake (New York: State University of New York Press, 1996), 53–72.

This would be true if Descartes' argument were empirical rather than logical. From a logical point of view, ‘feigned’ denial is as good as ‘sincere’ denial, since the sphere of the possible, not the actual, matters in logic. Hence, if Descartes can prove his existence as a thinking being even under an entirely speculative assumption that he has no body, then he has logically proved that the body is not necessary for his existence as a thinking being. In making this remark, I don't reject the possibility that Descartes may have lost control over his self-deception, but I'm emphasizing my claim that one should carefully distinguish between the psychological aspect and the logical aspect of Descartes' investigation.

⁸ Frankfurt expresses it very well: ‘The demon hypothesis does not simply refresh his awareness that he may be deceived in all the judgments at issue; it entails that he is deceived in all of them.’ (Op. cit. note 4, 86) Yet Frankfurt interprets this in Descartes' terms of an external deceiver (‘he is deceived’) and not as a process of self-deception.

⁹ Op. cit. note 1, 79–80.

¹⁰ Ibid., 80.

¹¹ Descartes, René, The Principles of Philosophy, translated by John Veitch (Whitefish: Kessinger Publishing, 2010 [1644]), 17.

I quote from this translation, since it is a more successful reflection of the original Latin text (emphasis mine, S.F):

René Descartes, Oeuvres de Descartes, Vol. VIII-1. Translated by Charles Adam and Paul Tannery (Paris: Librairie Philosophique J. Vrin, 1964a), 7.

The Cambridge translation, for example, is problematic at this point:

René Descartes, The Philosophical Writings of Descartes, Vol 1, translated by John Cottingham, Robert Stoothoff & Dugald Murdoch (Cambridge: Cambridge University Press, 1985), 194–195.

Descartes, it should be clear, speaks about a psychological experience rather than a logical recognition.

¹² Op. cit. note 1, 102.

¹³ Spinoza, as a Cartesian discipline, starts his Ethics with the idea of God and does not repeat Descartes' ‘mistake’.

See: Benedict Spinoza, Ethics, translated by W. H. White (Hertfordshire: Wordsworth Editions, 2001 [1677]).

¹⁴ Op. cit. note 1, 81.

¹⁵ Ibid., 85.

¹⁶ Bernard Williams notes that the Latin verb cogitare and the French verb penser have a wider meaning than the English verb to think. Bernard Williams, Descartes: The Project of Pure Enquiry (London: Routledge, 2005), 62.

¹⁷ Op. cit. note 1, 91.

¹⁸ Later in the investigation, he will distinguish between willing and thinking.

¹⁹ Ibid., 92.

²⁰ Ibid.

Descartes was attacked in relation to this psychological principle of truth. This is probably the reason why in Principle 45 of his later book, Principles of Philosophy, under the title ‘What Constitutes Clear and Distinct Perception’, he writes in an ironic yet apologetic manner that ‘there are indeed a great many persons who, throughout their whole lifetime, never perceive anything in a way necessary for judging it properly’.

Op. cit. note 11, Descartes 2010, 23.

²¹ Tlumak argues that the acknowledgment of God is the first metaphysical truth and the turning point of the Meditation, since God, as Eternal Being, is the only being that the certainty concerning its existence at any moment could be considered an irreversible truth. This is the reason why Descartes, after demonstrating God's existence, can rule out preposterous possibilities which enable metaphysical doubts. See: Jeffery Tlumak, ‘Certainty and Cartesian method’, In Descartes: Critical and Interpretive Essays, edited by Michael Hooker (Baltimore: The Johns Hopkins University Press, 1978), 40–73.

²² This is the rationalist idea of freedom upheld since Plato: real freedom means the freedom to act according to reason. Kant is, perhaps, the last great thinker who continues this line of thinking when he claims that the moral law expresses our freedom to obey our reason:

Immanuel Kant, Critique of Practical Reason, translated by Thomas Kingsmill, Abbott (Mineola: Dover Publishing. 2004 [1788]), 34.

²³ It is interesting to note that this is the first time in his epistemological investigation that Descartes mentions ethical terms such as good and bad or sin. This strengthens the interpretation that he considers his epistemological investigation to be an existential task.

²⁴ Op. cit. note 1, 115.

²⁵ This calls to mind Freud's definition of illusion: ‘Thus we call a belief an illusion, when a wish-fulfillment is a prominent factor in its motivation […]’

Sigmund Freud, ‘The future of illusion [1927]’, In The complete psychological works, Vol. XXI. Translated by James Strachey (London: The Hograth Press, 1961), 5–56, 31.

²⁶ Op. cit. note 1, 117.

²⁷ Ibid., 118.

²⁸ Ibid., 143.

²⁹ Ibid., 142.