The Certainty of the Cogito: A Modal Perspective 1 Descartes' intellectual trajectory, as articulated in his Discourse on the Method, shows his obsessional quest for certainty. It seems as though the quest for truth was, for him, the quest for certainty. We know that it led him ultimately to Cogito ergo sum (I think, therefore I am), the first proposition that he believed to be the most certain -certissima -of all. 2 However, what he meant by the word certissima is not clear. Does he simply

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... that it is, in an epistemological sense, the most secure or best justified of our beliefs? It should be noted that Descartes often refers to modal notions such as necessary and impossible when he talks about certainty. This indicates that his sense of certainty might be better construed from a modal than from an epistemological point of view. In what follows, I discuss the Cartesian Cogito to show that its privileged certainty derives from a certain impossibility that Descartes discovered delimited the essential part of our being. Probability and certainty