How did George Berkeley argue that physical objects are collections of ideas?

George Berkeley, an 18th-century Irish philosopher, argued that physical objects are collections of ideas through his doctrine of subjective idealism, famously summarized by the phrase esse est percipi ("to be is to be perceived").12

Berkeley’s argument rests on the following points:

• The Nature of Perception: He maintained that all qualities attributed to objects—such as hardness, color, or motion—are sense qualities. Because these qualities are experienced through the senses, they exist only when perceived by a mind or spirit.13
• The Syllogism: Berkeley supported his thesis with a logical argument: physical objects are things perceived by sense; things perceived by sense are ideas; therefore, physical objects are ideas.3
• Rejection of Matter: Unlike his predecessor John Locke, Berkeley denied the existence of a material substance "behind" or "underlying" these ideas. He argued that it is contradictory to conceive of matter as unsensed extension or motion, as these are themselves ideas that must be sensed to exist.34
• Divine Perception: To address why objects continue to exist when not perceived by humans, Berkeley argued that they persist in the mind of God, whose constant perception keeps the physical world in existence.3