When rationality reemerged in the 14th century after having decayed in the ancient Greece, it ultimately faced the same problem as that which caused its decay in the ancient Greece – to find an irrefutable truth – in order to defeat belief.
The great battle took place at Darwin’s publication of “On the Origin of Species”. Although all rationalists agreed that evolution is the most plausible explanation for the origin of the biological diversity, many of them felt that there was something awkward (inconsistent) with the model for it. However, since the victory for rationality over belief for the moment was more important than rational consistency, the rational advocates for the model argued that this problem must be solved later, and the protesters were run-over by a democratic acceptance of the model by the rational community.
About 50 years later, in 1901. Bertrand Russell demonstrated logically that naive set theory (actually finite classification) ultimately leads to paradox. He thereby revealed the inconsistency with Darwin’s model – it is actually paradoxically contradictory. (This fact had been known by members of the University of Göttingen before, but they didn’t publish it, possibly because it could harm rationality.)
After this, this problem was left hanging until the German Nazi Willi Hennig used Darwin’s model to promote the fundaments for race biology with what he called “the fundament for a phylogenetic classification”. About a decade later, his “fundament” was introduced to biological systematics, and after a fierce stride against it, was in the 80-ies democratically accepted by the biological systematics community under the name “cladistics”. By then, the problem had thus not been solved, but instead used to legitimate race biology.
At this point, we (rationalists) have to understand that this problem actually is what happens if we treat rationality as a belief, ie, if we believe in rationality. If we don’t understand this fact, then we will actually bury rationality. We (rationalists) have to understand that rationality can’t compete with belief (which also Karl Popper and Ludwig Wittgenstein explained).