Locke's Primary & Secondary Quality Distinction

Berkeley's Arguments against Primary and Secondary Properties

Jan 4, 2009

Locke theorised a distinction between the primary and secondary properties of objects which, with some adapting, can still survive its criticisms today.

Primary properties resemble the real properties of the object. Locke, in his book, An Essay Concerning Human Understanding, said they are "utterly inseparable from the body" and necessary for conception of it. Primary properties include: solidity, extension, figure, motion and rest, and number.

Secondary properties, Locke argues in An Essay Concerning Human Understanding, are "nothing in the objects themselves but powers to produce various sensations in us," and conceptually inessential. Secondary properties include: colour, temperature, smell, taste and sound.

Indirect Realism

Locke was an Indirect Realist. As Dancy explains in his book, Introduction to Contemporary Epistemology, Indirect Realism argues that "in perception [people] are indirectly aware of the physical [world]…in virtue of a direct awareness of internal, non physical objects." It means that someone's idea of an object resembles the actual object itself but they can only be aware of their idea itself; rather than the object.

Argument from Likeness

One issue raised by Berkeley in, Principles of Human Knowledge and Three Dialogues, was that "an idea can be like nothing but an idea." Since, according to indirect realism, only ideas can be directly perceived and not the objects themselves, perception of an object’s properties cannot resemble the real properties of that object unless it is also non physical. This is a big problem for Locke but it can be solved by changing the background theory of perception from indirect realism to direct realism which, as Dancy explains, holds that "in sense-perception [people] are directly aware of the…nature of the surrounding world."

Redefining Locke's Definitions

A more serious argument against Locke's formulation of Primary and Secondary properties is Berkeley's Argument from Relativity. This successfully destroys Locke’s distinction between primary and secondary properties. As a result Locke’s definitions must be refined:

1. The primary properties of an object are its intrinsic properties – the basic and essential elements that make it what it is by itself, rather than through association.

2. Secondary properties are relational properties of an object which depend not just upon it but also upon a perceiver.

With these new definitions extension, shape, motion and solidity are considered secondary qualities because they are relational; but, because an object retains each of these properties even when it is not being perceived, they must also be intrinsic, primary properties. It may seem somewhat paradoxical (to say extension, shape, motion and solidity are all primary and secondary qualities); however it is in what way they are conceived that clears up this ambiguity. Further explanation of this begins with Berkeley’s Conceivability Argument.

The Conceivability Argument helps to explain that extension, solidity, shape and motion are primary properties when conceived of through mathematics, and secondary properties when they are conceived through perception. For example if someone stood 200 meters away from a building its height is a primary property when considered as being "90 meters tall" but it is a secondary property when considered as the building's "height-as-they-see-it" (which may only be the size of their thumb from where they stand).

Berkeley's Attack on Abstract Ideas

The problem that conceiving of objects in a purely mathematical sense faces, from Berkeley’s point of view, is that it would require abstract ideas (ideas stripped of time and place) which Berkeley considers the primary causes of disturbance and doubt in philosophy. Berkeley's arguments against abstract ideas are not damning to such mathematical conception of objects though because modern mathematicians can conceive of universe consisting of 12 dimensions, so it is clearly plausible that people can also conceive of three dimensional properties in that mathematical sense as well.

References

The copyright of the article Locke's Primary & Secondary Quality Distinction in Epistemology is owned by Peter Burnham. Permission to republish Locke's Primary & Secondary Quality Distinction in print or online must be granted by the author in writing.