How do you become an Atheist?

[theVOID]

Would that interpretation of non-contingent truth be analogous to "red light means stop" whether there is anything to stop, or any meaningful definition of stop? If so, then non-contingent truth must be contingent upon the mind because the very notion of its non-contingency exists only as a concept in the mind.

No, "red light means stop" is a concept, you have to know the concept before a red light means stop, otherwise it's just a red light on a poll.