 Another candidate for a physical quiddity that Pereboom identifies is due to John Locke (1690). In Locke’s conception, solidity is the categorical basis for impenetrability, which is dispositional. Lockean solidity is “that which hinders the approach of two bodies when they move toward one another” (Locke 1690: II, iv, emphasis added). Lockean solidity is also what differentiates matter from space, and is a defining property of matter. On one plausible interpretation, Pereboom (2011: 97–100) suggests, Locke regards that property as an absolutely intrinsic property of matter and as a physical quiddity.