Descartes’ philosophy begins in doubt. The first step towards certainty, the Archimedean point from which the whole structure will grow, is the discovery of the existence of the self. At the beginning of Meditation II, reflecting on the evil genius posited at the end of Meditation I, Descartes observes: ‘Let him deceive me as much as he can, he will never bring it about that I am nothing so long as I think that I am something… 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’.
In the earlier Discourse (Part IV) and the later Principles of Philosophy (Part I §7 ), this proposition has the more familiar form, ‘I am thinking, therefore I exist,’ or, ‘ego cogito, ergo sum,’ in its Latin formulation. Here, it is called the Cogito Argument. There is considerable discussion about how exactly Descartes thought this argument functions. There are two strains of interpretation that derive directly from his texts. In the Second Replies, Descartes observes that ‘when we become aware that we are thinking things, this is a primary notion which is not derived by means of any syllogism’.
This suggests that the Cogito Argument is known immediately by direct intuition. In the Principles (Part I §10), however, Descartes notes that before knowing the Cogito, we must grasp not only the concepts of thought, existence and certainty, but also the proposition that ‘it is impossible that that which thinks should not exist’. This suggests that the Cogito is a kind of syllogism, in which I infer my existence from the fact that I am thinking, and with the premise that whatever thinks must exist.
Recent analytic philosophers have also been attracted to the Cogito, trying to understand its obvious allure through speech act theory and theories of demonstratives (Hintikka 1967; Markie 1992 ). These accounts, however, are distant from anything that Descartes himself conceived. There is also some confusion about what the conclusion of the Cogito Argument is supposed to be. In the body of Meditation II, Descartes clearly establishes the existence of the self as a thinking thing or a mind.
But the title of Meditation II, ‘The nature of the human mind, and how it is better known than the body’ suggests that Descartes believed that he had established that the nature of the human mind is thought. Further still, in parallel texts in the Discourse (Part IV) and the Principles (Part I §7–8 ), Descartes suggests that the Cogito establishes the existence of a thinking substance distinct from the body, though in the text of Meditation II, this seems to be denied.
Though most closely associated with Descartes, the Cogito Argument may not be altogether original. A number of Descartes’ contemporaries, both during his life and afterwards, noticed the connection between the Cogito and similar formulations in Augustine (see Augustine §2). However, what was important to Descartes about the Cogito is the foundational role it plays in his system. For Descartes, it is ‘the first thing we come to know when we philosophise in an orderly way’ (Principles: Part I §7 ).
Common sense might think that the physical world of bodies, known through sensation, is more accessible to us than is the mind, a thinking thing whose existence is established, even though we have rejected the senses. But, as Descartes argues in Meditation II using the example of a piece of wax, despite our prejudices, bodies are not conceived through the senses or the imagination but through the same process of purely intellectual conception that gives us the conception of ourselves as thinking things.
Furthermore, knowledge of the external world is less certain than knowledge of the mind, since whatever thought could lead us to a probable belief in the existence of bodies will lead us to believe in the existence of the self with certainty. The project, then, is to build the entire world from the thinking self. It is important here that it is not just the mind that is the foundation, but my mind. In this way, the starting place of philosophy for Descartes was connected with the rejection of authority that is central to the Cartesian philosophy. In beginning with the Cogito, we build a philosophy detached from history and tradition.