|Cogito: "I think". According to Descartes the prove that I exist, because the subject may even reach the doubts about its existence just by thinking and the subject must exist in order to think. Kant speaks of the "I think" that must accompany all my ideas/conceptions/notions/presentations, in order to make them my representations.See also thingking, existence, justification, representation.|
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cogito / Prior: you can think that you think something and this could be the only thing you think, but not the only one that is true and then this is not necessarily true - then there must be something else real than what you think - it can never be the only imaginary proposition that there are true propositions.
Objects of thought Oxford 1971
Arthur N. Prior
Papers on Time and Tense 2nd Edition Oxford 2003