Three Dialogues Between Hylas and Philonous

"Three Dialogues between Hylas and Philonous is a book written by George Berkeley in 1713.

"The most important concepts in the Three Dialogues are: perceptual relativity, the conceivability ("master") argument and Berkeley's phenomenalism. The perceptual relativity argument is 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, then shape must not be an objective feature.

"Hylas is understood to represent John Locke, Berkeley's primary contemporary philosophical adversary. A Hylas is featured in Greek mythology: in the Dialogues the name Hylas is derived from an ancient Greek word for matter which Hylas argues for in the dialogue.

"Philonous translates as lover of mind and represents Berkeley himself."

Source: http://en.wikipedia.org/wiki/Three_Dialogues_between_Hylas_and_Philonous