You can only know what is true. For example, everybody knows the statement “If p is true then p is true” is true (just why in a moment). You can believe what is true or what is false. Thus many believe the statement “President Obama has never engaged in demagoguery” which is false (again, just why in a moment).
Rene Descartes famously wondered just what he really knew and what might be mere belief. That is, what is certain and what might be doubted. According to Stanford’s Encyclopedia of Philosophy:
Descartes understands doubt as the contrast of certainty. As my certainty increases, my doubt decreases; conversely, as my doubt increases, my certainty decreases. The requirement that knowledge is to be based in complete, or perfect certainty, amounts to requiring a complete absence of doubt — an indubitability, or inability to undermine one’s conviction. Descartes’ methodic emphasis on doubt, rather than on certainty, marks an epistemological innovation. This so-called â€˜method of doubtâ€™ will be discussed below
As nearly everybody who has attended at least one college course has heard, Descartes stripped away every piece of information for which he could express the least doubt. Again, the SEP (quoting Descartes):
I have convinced myself that there is absolutely nothing in the world, no sky, no earth, no minds, no bodies. Does it now follow that I too do not exist? No: if I convinced myself of something then I certainly existed. But there is a deceiver of supreme power and cunning who is deliberately and constantly deceiving me. In that case I too undoubtedly exist, if he is deceiving me; and 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. So after considering everything very thoroughly, 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. (Med. 2, AT 7:25)
All will recognize this as part of the (in)famous cogito ergo sum. Although this is too summary, Descartes argued that this was the most fundamental or basic truth. Now, other truths existed or could be deduced from the basic truth, but the cogito (Descartes thought) begins it all.
Of course, it is true that “Because I think I therefore exist,” but in saying that, I (and Descartes) am actually admitting to more knowledge than just this statement. That is, I—and I say “I” because the cogito allows me to doubt “you”—am implicitly arguing that I know more than just that I exist. Can you see it? It is yet another lovely proof that empiricism is false. Empiricism, as Scruton defines it, is the desire that:
(i) All claims to knowledge are based on knowledge of experience: experience is the ‘foundation’ of knowledge.
(ii) Experience can provide such a foundation only if my beliefs about my present experiences are immune to error…
(iii) But my experience does provide a foundation, since the realm of experience is ‘set apart’ from the physical world: it is a realm off ‘privileged access’ where (and I alone) am sovereign…
Now it might appear that the cogito is known by experience, just as we know that the “demagoguery” statement is false from experience. I experience me and from that deduce that I must exist. But that sentence gives the game away—can you see it yet?—for how can I know how to deduce truths from experience? To make it clear: I start with the knowledge of me, but then I must use certain truths of logic to deduce from my observation that I in fact exist. But how did I know those truths of logic, the rules that allow and produce deductions?
I cannot know these truths from experience and there isn’t any way to bootstrap this knowledge to use in the proof of the cogito (and if there isn’t a way for me to do this, there is no way for anybody; there cannot be an infinite regress; the process has to begin somewhere). Just as I cannot know from experience that for any p that “If p is true then p is true” is true. I just know it (and other similar statements) are true.
Therefore, we must come pre-built with these (and other) truths, which is a long way of saying that truth exists and thus these truths must be acknowledged. But where do those pre-built truths come from? Well, the answer is obvious—which is why some desire empiricism.
A bit busy this week with my new gig. I’ll be a little slow answering comments.