Thank you for the answer. I read the Rabbi’s column, but I wasn’t convinced. The Rabbi argues that all forms of the claim are “either way” arguments, and such arguments can be resolved simply with a third option (the Rabbi brings there the example of the bald king of France), and then says that in fact the cogito argument is an observation like any other observation, though a stronger observation than observation of material objects.

But I, in my humble way, would like to challenge that and say that observation and existence are one and the same in the case of the cogito. I try to tell myself that I do not exist. Theoretically, I can understand this with regard to “I do not exist materially,” or even “I do not exist as Moshe Zochmir with a consciousness possessing characteristics x, y, z,” but when I try to tell myself that I do not exist as a thinking entity, I simply cannot understand what I am even saying. I’m not enough of an expert in logic to say that this is logical certainty, but existential certainty there certainly is here.