Being a serial debater with people who have fallen victim to Jedi Mind Tricks I often encounter claims that “we can’t just assume we are rational.” I’ve tried to explain what’s wrong with these types of claims before on multiple occasions but given it’s something I find a great many have trouble articulating, and it’s again come up in my private and public debates of late, I think it’s worth another go. I think this will be a more clear explanation of the issues but I also must say I owe this idea to a friend who shall not be named (unless he later decides he wants to be).
While some who say things like “we can’t assume we are rational” are abusing this nod towards radical skepticism to cast doubt on the validity of arguments, others are using it to argue “only god can grant us rationality” but both are misguided for the same reason. In order to make an argument for some conclusion the argument must contain a set of premises, P1, P2, P3,… PN. People who argue we can’t just assume rationality because nothing guarantees that assumption seem to want to claim that unless we have 100% certainty of something we have no basis for having confidence in the conclusion of the argument. After all, P1-PN doesn’t contain a clear guarantee that we are rational, nor does it contain a guarantee of infallibility, so without the absolute baseline we can’t trust our faculties to even have followed the argument. However this is extremely confused thinking.
Before any argument can begin we all make the assumption that we are rational and that rationality can be brought to bear on the subject at hand, call this P0. Every argument made implicitly assumes P0 before beginning and P0 assumes, among other things, logical consistency, inference, induction and the axioms of deduction and rationality. If you remove this premise you can’t make any rational inference or argument at all. Literally all words would be meaningless and even if they weren’t no statement would infer any other statement.
Without first assuming that you are rational and that logical inference is legitimate you can’t get to the existence of anything, including god, so you can’t then use god to say you can be certain that those very same assumptions you just made are 100% sound. This also means you can’t assume you are rational in order to prove we have no reason to believe we are rational. Simply put, you can’t make an argument which refutes that we are rational nor can you make an argument that proves the axioms of rationality because you’d first need to assume those axioms to even begin.
This is why all sci-fi, conspiracy theory or presuppositional scenarios in which people argue, for whatever reason, we have no basis to assume we are rational are self-defeating. Nothing can get you out of this, we all must make these assumptions or give up thought entirely. There are no other options.