What are you absolutely certain of? Of what are you sure without any conceivable doubt? What is true no matter what? What is necessarily true? Just one thing. Whatever. As long as you’re sure.
I’ve been playing the game for a while and I’ve been shocked to be unable to answer the question. Now, of course I’m familiar with Hume‘s skepticism (you don’t really know an apple is going to fall, you’ve just seen all similar objects fall before at similar conditions but you don’t know) and I thought I knew how dear truth was but lately, slowly, I’ve started to realize that not even reason or logic are to be trusted.
Let’s start by quickly demolishing every statement about experience, like, say, that you are, well, you, that you broke your knee when you were fifteen, that your mother exists, that other people exist (solipsism). The usual shortcut is just to ask you how do you know it isn’t all a dream, but I prefer Russell‘s more imaginative version, the extreme omphalos hypothesis: how do you know that the world wasn’t created five seconds ago, set in motion, and with fake memories? Clever, huh?
OK, that sweeps off a good big swath of possible answers. As for reason/logic, its problem is that it’s either redundant or not binding at all. But don’t 2 + 2 = 4 whatever fucking nightmare the world might turn out to be? How could time or space not exist? My gosh, can you look me in the eye, and tell me that numbers aren’t infinite? How demented do you need to be to doubt Aristotle’s syllogisms, the very rules of thought (if it’s true that humans are mortal and that Socrates is human, Socrates has to be mortal!)?
But it turns out these conceptual statements aren’t certainties either. When you probe them further, carefully, rigorously, you realize that to advance you have to start defining. If you do it conscientiously, defining or making explicit even the dumbest, most-taken-for-granted assumptions you start to realize that 2 + 2 = 4 because you said so, because you assumed your conclusion from the get-go, and your statements are true in the same empty way that a bachelor can’t be married or a car has to be an automobile too. Yes, it’s a kind of truth, but a rather measly one.
The other thing that usually happens when you probe concepts is one of the most wondrous experiences I know of, exhilarating and unnerving at the same time, dizzying. I call it sense of could. It means taking an entrenched concept and realizing it is not necessarily so, discovering your singularity is just an instance of something subtler, deeper, finding out your rose is one among thousands, seeing that what you thought fixed is just another degree of motion.
Like when Cantor found out there are many kinds of infinities, some bigger than others (!). Like when you realize logic isn’t the complete science Kant thought and open the gates to the non-classical logics. Like when you probe the very fabric of the universe by looking for primitives to space and time. More worldly, like when you question your ethics, your religion, your politics, and you find only possibility where you were looking for necessity.
Now, those two options, redundancy and non-necessity, are the ones I’ve always stumbled upon but I don’t really know that happens for every concept. Or neither do I know if you can dismiss all experience in one fell stroke. That is, I’m, of course, not even sure that you can’t be sure of anything. Would you care volunteering an answer? (Or a question?)