"Recently we got in a huge fight because he was trying to demonstrate an example of the Hegelian concept of the "unity of opposites" (whatever that means) by claiming that right and left hands are opposite but also identical. I told him this is just wrong and that right and left hands are not "identical" in any meaningful sense (chirality is a basic concept in geometry/group theory: left and right hands are not superimposable). He kept putting his hands together and tried to show how they were "identical" and kept failing (because they're not) and then got angry and stormed out of the house. I haven't seen him since (this was about a day ago) and texted him and haven't heard back."