Troglodyte philosopher
From chapter 10 of the Tale of a Tub

The Troglodytes were the races dwelling in caves, described by some of the ancient historians. The word occurs in Rabelais, but not in the same sense as here. Montesquieu uses it in the Lettres Persanes to describe a people with peculiar ideas and customs of their own. Here Swift uses it in the sense of the typical cynic in his tub.