How did George Berkeley challenge the idea of a reality independent of perception?

George Berkeley challenged the idea of a reality independent of perception by arguing that the existence of material objects is entirely dependent on being perceived by a mind. His fundamental doctrine, esse est percipi ("to be is to be perceived"), posits that sensible objects are nothing more than collections of ideas or sense-data.12

Berkeley rejected the notion of an imperceptible "material substrate"—a concept supported by John Locke—arguing that because all human knowledge is derived from perception, it is impossible to know or justify the existence of anything that exists outside of the mind. He contended that properties such as extension, color, and impenetrability exist only as ideas within a percipient mind.13

Through his "master argument," he highlighted that one cannot imagine an object existing unperceived without failing to account for the perceiver, as the very act of imagining an object requires a mind to conceive of it. While Berkeley maintained that objects remain "perceivable" even when not currently being observed by a specific individual, he insisted that their continued existence is still fundamentally related to perception, rather than an independent, mind-independent material reality.1