The question of what is a mathematical object was a deep source of debate in the last part of the eighteenth and first part of nineteenth century. There has only been at best a partial resolution, caused in part by Godel's work in logic and in part by exhaustion.
What's the meaning of "by exhaustion"?
- Despair people feel despair in solving the question
- Tired people feel tired to solve the question
- The question was exhausted