Key Arguments

• Ideas of substances are intended to represent things existing outside of us, so their reality depends on agreeing with actual existence.
• Fantastical ideas of substances (like a centaur or a yellow, malleable body lighter than water) consist of collections of simple ideas that were never found united in any real substance.
• Even if such imaginary substances could theoretically exist, they must be considered barely imaginary because they conform to no known existing pattern.

Source Quotes

Complex ideas of substances are real, when they agree with the existence of things. Thirdly, Our complex ideas of substances, being made all of them in reference to things existing without us, and intended to be representations of substances as they really are, are no further real than as they are such combinations of simple ideas as are really united, and co-exist in things without us. On the contrary, those are fantastical which are made up of such collections of simple ideas as were really never united, never were found together in any substance: e.g.. a rational creature, consisting of a horse’s head, joined to a body of human shape, or such as the centaurs are described: or, a body yellow, very malleable, fusible, and fixed, but lighter than common water: or an uniform, unorganized body, consisting, as to sense, all of similar parts, with perception and voluntary motion joined to it.

Thirdly, Our complex ideas of substances, being made all of them in reference to things existing without us, and intended to be representations of substances as they really are, are no further real than as they are such combinations of simple ideas as are really united, and co-exist in things without us. On the contrary, those are fantastical which are made up of such collections of simple ideas as were really never united, never were found together in any substance: e.g.. a rational creature, consisting of a horse’s head, joined to a body of human shape, or such as the centaurs are described: or, a body yellow, very malleable, fusible, and fixed, but lighter than common water: or an uniform, unorganized body, consisting, as to sense, all of similar parts, with perception and voluntary motion joined to it. Whether such substances as these can possibly exist or no, it is probable we do not know: but be that as it will, these ideas of substances, being made conformable to no pattern existing that we know; and consisting of such collections of ideas as no substance ever showed us united together, they ought to pass with us for barely imaginary: but much more are those complex

On the contrary, those are fantastical which are made up of such collections of simple ideas as were really never united, never were found together in any substance: e.g.. a rational creature, consisting of a horse’s head, joined to a body of human shape, or such as the centaurs are described: or, a body yellow, very malleable, fusible, and fixed, but lighter than common water: or an uniform, unorganized body, consisting, as to sense, all of similar parts, with perception and voluntary motion joined to it. Whether such substances as these can possibly exist or no, it is probable we do not know: but be that as it will, these ideas of substances, being made conformable to no pattern existing that we know; and consisting of such collections of ideas as no substance ever showed us united together, they ought to pass with us for barely imaginary: but much more are those complex

Key Concepts

• Our complex ideas of substances, being made all of them in reference to things existing without us
• are no further real than as they are such combinations of simple ideas as are really united, and co-exist in things without us.
• those are fantastical which are made up of such collections of simple ideas as were really never united, never were found together in any substance
• they ought to pass with us for barely imaginary

Context

Locke establishes the empirical requirement for the reality of substance concepts, contrasting them with the purely logical requirements for mixed modes.