“Hume on Space (and Time)” explores the way in which Hume’s presentation of space-time depends upon Leibniz’s. Hume’s interaction with the Leibniz-Clark correspondence challenges him to address the simplicity argument in regard to his view on the immateriality of space. Mijuskovic concludes:
As Leibniz had insisted that our thoughts are ultimately simple, unified, and indivisible (because the monads are), so Hume held that the visible and tangible points, which have no dimensions, are ultimately qualitative simples and ideal, that is, mental existences. 
Although Hume did not agree about the nature of the mind as a unified, simple substance, his presentation of thoughts illustrates the strength of the simplicity argument’s premise embraced by both sides of the larger debate regarding the nature of mind. He cannot overlook the fact the objects (thoughts) of the bundle of perceptions (mind) do not possess an extended or material existence. This concession makes Hume’s philosophy of mind, in part, a candidate for study in the history of the simplicity argument.