I think, therefore I am

I am in doubt as to the propriety of making my first meditations in the place above mentioned matter of discourse; for these are so metaphysical, and so uncommon, as not, perhaps, to be acceptable to every one. And yet, that it may be determined whether the foundations that I have laid are sufficiently secure, I find myself in a measure constrained to advert to them.

I don’t know if it’s proper to share my thoughts as they are so metaphysical and unusual that not everyone may appreciate them. However, in order to test these ideas, I find I need to call attention to them.

I had long before remarked that, in relation to practice, it is sometimes necessary to adopt, as if above doubt, opinions which we discern to be highly uncertain, as has been already said; but as I then desired to give my attention solely to the search after truth, I thought that a procedure exactly the opposite was called for, and that I ought to reject as absolutely false all opinions in regard to which I could suppose the least ground for doubt, in order to ascertain whether after that there remained aught in my belief that was wholly indubitable.

Often in order to test a theory or process, we need to put our faith in opinions/ideas that we think are doubtful. However I want to test what is true, and to do this I need to employ the opposite method – discard all ideas in which I have even the slightest doubt, so I can find whatever (if anything) is left.

Accordingly, seeing that our senses sometimes deceive us, I was willing to suppose that there existed nothing really such as they presented to us; and because some men err in reasoning, and fall into paralogisms, even on the simplest matters of geometry, I, convinced that I was as open to error as any other, rejected as false all the reasonings I had hitherto taken for demonstrations;

and finally, when I considered that the very same thoughts (presentations) which we experience when awake may also be experienced when we are asleep, while there is at that time not one of them true, I supposed that all the objects (presentations) that had ever entered into my mind when awake, had in them no more truth than the illusions of my dreams.

Since our senses sometimes deceive us, I’m rejecting anything I can observe with them. Also, since people make errors and I am no better, I’m rejecting any conclusions I have drawn from any observations I have made. And because the ideas I have when I am awake I can also have while I sleep, I am rejecting them as well since they could just be illusions like my dreams.

But immediately upon this I observed that, whilst I thus wished to think that all was false, it was absolutely necessary that I, who thus thought, should be somewhat; and as I observed that this truth, I think, therefore I am (COGITO ERGO SUM), was so certain and of such evidence that no ground of doubt, however extravagant, could be alleged by the sceptics capable of shaking it, I concluded that I might, without scruple, accept it as the first principle of the philosophy of which I was in search.

Immediately after rejecting all these senses, conclusions and ideas, I realised that even though I wanted to think that everything was false, it was necessary that I, who was doing the thinking, must exist in some form. I saw that this truth “I think, therefore I am” was so certain that no doubt, however outlandish, could shake it. I concluded that I could accept this as the first principle in my search for what is true.