Abstract
John Locke's first letter to Stillingfleet addresses a number of important philosophical topics, including the idea of substance, knowledge without clear and distinct ideas, the existence of spiritual substances, the ontological argument for the existence of God, and the real essences of things. He notes that his Essay does not contain a single argument against the doctrine of the Trinity, and indeed, he says that he wrote the entire book "without any Thought of the controversy between the Trinitarians and Unitarians". One episode in Locke's second letter that nicely illustrates its overall character is a 48‐page discursion in which he recounts conversations that he had with some friends about Stillingfleet's efforts to explain certain key concepts. Locke's second letter focused mainly on Stillingfleet's muddledness, and on the thinness of the pretext for involving Locke in the first place. Stillingfleet's reply to each of these letters is presented in this chapter.