In Philosophy Now, Peter Adamson on philosophers thinking badly.

The historian may protest that to be interested in Aristotle, al-Kindi, or Kant, is unlike voting for a politician: it need involve no approval of the author’s worldview. I’ve met many experts in Aristotelian cosmology, and not one of them has thought that the Sun orbits the Earth, as Aristotle did. So we might treat the bigotry of the past the way we treat the scientific mistakes of the past. That is, rather than detaching hateful remarks from the rest of the theory, we detach ourselves, offering an objective analysis of these thinkers’ ideas without ever adopting those ideas as our own. This will often involve situating the thinkers in their historical context. We might for example note – as a historical observation, not as a matter of praise or blame – that when Plato argued in the Republic that women can do everything men can do, but not so well, he was being unusually ‘feminist’ for his time – while simultaneously being sexist by modern standards. This seems a reasonable solution, but it will not be enough for those philosophers who do not see themselves as ‘mere’ historians, but seek truth in historical works. Most notorious in this regard is the case of Heidegger. There is an ongoing debate as to whether his Nazism effectively poisons his thought as a whole, making it off limits as a source of philosophical inspiration.