Key Arguments

• The mind notices that certain simple ideas constantly go together and groups them under one name for convenience and quick communication.
• Because human understanding cannot imagine how simple ideas (qualities) can subsist by themselves, we habitually assume they must rest in and result from some underlying support.

Source Quotes

Ideas of particular substances, how made. The mind being, as I have declared, furnished with a great number of the simple ideas, conveyed in by the senses as they are found in exterior things, or by reflection on its own operations, takes notice also that a certain number of these simple ideas go constantly together; which being presumed to belong to one thing, and words being suited to common apprehensions, and made use of for quick dispatch, are called, so united in one subject, by one name; which, by inadvertency, we are apt afterward to talk of and consider as one simple idea, which indeed is a complication of many ideas together: because, as I have said, not imagining how these simple ideas can subsist by themselves, we accustom ourselves to suppose some substratum wherein they do subsist, and from which they do result, which therefore we call substance. 2.

Key Concepts

• a certain number of these simple ideas go constantly together
• not imagining how these simple ideas can subsist by themselves, we accustom ourselves to suppose some substratum wherein they do subsist
• which therefore we call substance.

Context

Locke explains the psychological origin of our concept of substances, showing it arises from cognitive habit and linguistic convenience rather than direct perception.