Claiming that concepts have some definite, if abstract, existence, is how not magical and flippant? They too are ambiguous, as is your example definition "the i

Claiming that concepts have some definite, if abstract, existence, is how not magical and flippant? They too are ambiguous, as is your example definition "the inner angles of triangle must sum to 180 degrees". It depends on euclidean geometry, on another concepts like line and points, and many other concepts possibly not yet invented. And it's all just a matter of convention, humans can follow conventions but so do computers. By the way, I myself don't think in the rigorous way you describe, either. And I can observe many humans don't too.