But if you want a serious answer, I'll say humans are wired for both thinking and counting at the factory. Logic and arithmetic are attempts to systematize these into formal systems that can be expressed symbolically and manipulated according to fixed rules that are always right and never change. But common sense tells us nothing is always right, and everything changes.

But eventually we learned that we can't be trusted to rely on "common sense" because it doesn't always work. In fact, it rarely works as well as we expect it to.

There's a story that the Hottentot language doesn't have a word for any number greater than 3. They count "1, 2, 3, many". To be fair, in their world, this was all they really needed.

But there comes a point when you really need to believe that 5+7 has to be the same as 7+5 and that 7x5 has to be the same as 5x7, but that 2x(3+4) is different than (2x3)+4. And to convince yourself of that, you need logic.