I had a professor at Michigan (60 years ago) who told a class that, "At Michigan critical thinking is the most important product." It was some science class or other and his remark was given as an aside. Still it is one of my most vivid memories.

I would argue that almost no schools at any level teach critical thinking these days. I don't believe thay did when I was at university.

Critical thinking depends on initial concepts. If there are any postulates then the course of thinking is already impredicative and petitio principii is the inevitable result. Fruit of the poisoned tree.

The only way to engage in truly valid argument is to avoid postulates entirely. Can that be done?

It can be done. It is subtle and therefore difficult but it can be done.

The beginning can be made by observing that the world (you could call it existence) cannot be denied. It cannot be denied because - what would be doing that? Denial of the world only affirms the world.

But there is a problem . . .

We have begun with an observation. This observation seems to presume, to imply, the existence of an observer. The problem with that is that no observer has yet been objectified. And until a final observer has been objectified nothing has been objectified - as objectification always implies a residuum.

This leaves us unable to argue either existence or nonexistence. And that is our starting point.

Can a world be built from this beginning? Indeed it can be. Nature does it and the way nature does it can be described all the way into this postulate-free beginning.