Three Dialogues between Hylas and PhilonousIn Opposition to Sceptics and AtheistsGeorge BerkeleyThree Dialogues between Hylas and Philonous is a book written by George Berkeley in 1713.Three important concepts discussed in the Three Dialogues are perceptual relativity, the conceivability/master argument ("master argument" was coined by Andr Gallois), and Berkeley's phenomenalism.Perceptual relativity argues that the same object can appear to have different characteristics (e.g. shape) depending on the observer's perspective. Since objective features of objects cannot change without an inherent change in the object itself, shape must not be an objective feature.Berkeley uses Hylas as his primary contemporary philosophical adversary. Hylas is featured in Greek mythology and is understood to represent John Locke. In the Dialogues, the name Hylas is derived from an ancient Greek word for "matter," which Hylas argues for in the dialogue.Using Philonous, Berkeley argues his own metaphysical views, which were first developed in his earlier book A Treatise Concerning the Principles of Human Knowledge. Philonous translates as "lover of mind."