 Arthur Collier was a much more obscure clergyman than Berkeley. He published his Clavis Universalis: Or, A New Inquiry after Truth, Being a Demonstration of the Non-Existence, or Impossibility, of an External World in 1713, the same year that Berkeley’s Principles of Human Knowledge appeared, and three years after Berkeley’s Three Dialogues; however, he states that he had originally conceived his position a decade earlier, so before he could have read Berkeley. Although the work was not widely read, it was translated into German by Johann Christian Eschenbach in 1756, and then noticed by Thomas Reid and following him Dugald Stewart. It was republished in English in 1837 along with Collier’s other philosophical work, A Specimen of True Philosophy, in a collection of Metaphysical Tracts edited by Samuel Parr, and then again in 1909, edited with an introduction by Ethel Bowman. By “external” Collier meant “independent, absolute, or self-existent”, and his position is that “all matter, body, extension, &amp;c.” (which he also frequently calls “expansion”) depends “on mind, thought, or perception, and that it is not capable of an existence, which is not thus dependent” (Collier 1713 [1909: 6]). Collier’s position is thus full-throated idealism, which he emphasizes is neither skepticism nor a denial that bodies exist, but the position that 