A Treatise Concerning the Principles of Human Knowledge

Berkeley's Principles is the founding text of modern subjective idealism. Every later idealist tradition — Kant's transcendental, Hegel's absolute, Schopenhauer's representational — engages with the Berkeleyan starting point.

"Their esse is percipi, nor is it possible they should have any existence out of the minds or thinking things which perceive them." (Principles §3)

Despite his idealist conclusion, Berkeley is a thoroughgoing empiricist about the origin of ideas — Locke is his starting point. The path from Locke's empiricism to Berkeley's immaterialism shaped Hume's further radicalisation.

"It is evident to anyone who takes a survey of the objects of human knowledge, that they are either ideas actually imprinted on the senses..." (Principles §1, opening)

Berkeley's analysis of physical objects as bundles of ideas perceived under regular sequences is the historical fountainhead of phenomenalism, from Mill and Mach through the early Russell.

"The table I write on... I say exists, that is, I see and feel it; and if I were out of my study I should say it existed — meaning thereby that if I was in my study I might perceive it." (Principles §3)

Berkeley was an Anglican bishop, and his immaterialism is in part an apologetic strategy: matter's removal makes God's providential sustenance of the world directly visible.

"The very same principles which at first view lead to scepticism, pursued to a certain point, bring men back to common sense." (Principles, Preface)

Kant explicitly distinguishes his transcendental idealism from Berkeley's "empirical" idealism (in the B-edition Refutation of Idealism), but the tradition Kant founds is unimaginable without Berkeley's prior move.

"To exist is to be perceived; and that things have no existence distinct from being perceived." (paraphrasing Principles throughout)

A genuine typological resonance noted by contemporary philosophers (David Chalmers): if reality is a structure of perceptions sustained by a coordinating mind, then Berkeley's metaphysics is structurally close to certain simulation theories — with God playing the role of the simulator.

"All those bodies which compose the mighty frame of the world have not any subsistence without a mind." (Principles §6)