Slots in Universals

Slot theory is the view that (i) there exist such entities as argument places, or ‘slots’, in universals, and that (ii) a universal u is n-adic if and only if there are n slots in u. I argue that those who take properties and relations to be abundant, fine-grained, non-set-theoretical entities face pressure to be slot theorists. I note that slots permit a natural account of the notion of adicy. I then consider a series of ‘slot-free’ accounts of that notion and argue that each of them has significant drawbacks.