One philosopher argued, with a straight face, that time itself doesn't exist
In his 1908 paper, J. M. E. McTaggart argued that our ordinary idea of time is self-contradictory: every event must be simultaneously future, present, and past, which is logically incoherent unless you smuggle in a second timeline to explain the shift — leading to an infinite regress. His conclusion that time is 'unreal' remains one of the most argued-over positions in philosophy of time.