Three Dialogues Between Hylas and PhilonousGeorge Berkeley

The Three Dialogues (1713) restate the argument of the Principles of Human Knowledge in conversational form. Hylas (from the Greek hylē, matter) defends the existence of material substance; Philonous (lover of mind) dismantles him. Over three days of argument, Berkeley leads the materialist through every available defense and closes each exit.

The first dialogue attacks the distinction between primary and secondary qualities. If heat, color, and taste exist only in the mind (as the materialists themselves concede for secondary qualities), then extension, figure, and motion are equally mind-dependent. The second dialogue considers whether matter might exist as an unknown substratum or occasion of ideas, and finds each formulation either contradictory or empty. The third dialogue addresses objections: that idealism makes the world unreal, that it contradicts science, that it leads to skepticism. Berkeley's reply is that his position is the true defense of common sense, because it takes the perceived world seriously rather than positing an imperceptible reality behind it.

The dialogues are among the most readable works in early modern philosophy, and they force a question the tradition has never fully settled: what exactly do we mean by "matter"?