Three Dialogues Between Hylas and Philonous

Taking the form of a dialogue, the book was written as a response to the criticism Berkeley experienced after publishing A Treatise Concerning the Principles of Human Knowledge.

[1] Three important concepts discussed in the Three Dialogues are perceptual relativity, the conceivability/master argument[a] 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.

[3] This foreshadowed his chief philosophical work, A Treatise Concerning the Principles of Human Knowledge (1710), which, after its poor reception, he rewrote into the Three Dialogues (1713).

In The First Dialogue, Hylas expresses his disdain for skepticism, adding that he has heard Philonous to have "maintained the most extravagant opinion that ever entered into the mind of man, to wit, that there is no such thing as material substance in the world.

He then moves on to primary qualities such as extension and shape, and likewise argues that they, too, are dependent entirely on one's perception and perspective (e.g., From a distance, a great mountain appears to be small, and the shape of a thing may change dramatically under a microscope: "You may at any time make the experiment, by looking with one eye bare, and with the other through a microscope"[5]).

Hylas's view of matter (which has its origin in the Platonic theory of forms [1], or abstract entities that exist outside of the sensible world)[citation needed] is systematically destroyed by Philonous (Berkeley).