I was referring to the crisis in the early 20th century, when the paradoxes and inconsistencies in the foundations of mathematics became too troublesome to igno

I was referring to the crisis in the early 20th century, when the paradoxes and inconsistencies in the foundations of mathematics became too troublesome to ignore. The crisis was eventually resolved, but the mathematics that arose from it was more limited in scope than what earlier mathematicians had hoped. That is usually not a major concern if you work in mathematics, but it was a significant change in the understanding of the nature of truth.