well I agree that utility is discovered. and as to truth? I am a fan of Xenophanes:

As for certain truth no [wo-]man knows it, ... even if by chance s/he were to utter The Final Truth, they would themselves not know it: for all is but a woven web of guesses.

Still it seems that nothing is "invented" here. Its true that the set of all possible axioms are not well understood, just as the details of the set of all primes are not understood. Yet both are enumerable.... waiting for their properties and consequences to be 'discovered' by us when we gaze upon them and consider them. (I am presuming that all axioms can be expressed as a paper in english, and the space of all English texts is just as enumerable as the primes are.)

this is the sense that I mean discovered.

I cannot really make out a sense in which it is invented and did not exist implicitly prior to this 'invention'