Apparently to arrive at truth – you have to have a common method of determining the answer.

You have to use a method that anybody on earth could come to the same conclusion. Otherwise no one in the world could be judged. Everyone could say I thought the other belief system was right.

You can’t use scriptures because each religion disagrees with the scriptures of the other. Unless you find out the which are true scriptures – but let’s leave that aside for now.

You can’t flip a coin. Because that is pot luck.

You can’t use feelings because one person could feel a is right while someone else could feel b is right.

So the only way one can determine who is right is through objectivity and logic. G-d gave us a brain to think. We must use it objectively – putting our feelings aside – to arrive at the truth.

See : find G-d through logic

See here : For Finding Truth of Torah through Logic

If you want attestation of the truth of the Jewish Torah – through science, Bible Codes, logic and archaeology see:
the discovery seminar

Gentiles who want to know what the Torah expects of them – see the 7 Noahide laws