The most horrifying journey, this is what doubting 'everything' does.

[vulcanlogician]

Explain me what an axiom is, and how it possibly is a source of knowledge. I would like to hear it.

An axiom or postulate is a statement that is taken to be true, to serve as a premise or starting point for further reasoning and arguments. The word comes from the Greek axíōma (ἀξίωμα) 'that which is thought worthy or fit' or 'that which commends itself as evident.'[1][2]

The term has subtle differences in definition when used in the context of different fields of study. As defined in classic philosophy, an axiom is a statement that is so evident or well-established, that it is accepted without controversy or question.[3] As used in modern logic, an axiom is simply a premise or starting point for reasoning.[4]

https://en.wikipedia.org/wiki/Axiom

An axiom is a starting point for reasoning. You actually can't reason at all without at least one axiom.