Human Understanding

Few, if any, books have had as great an impact on the history of thought on the nature of human consciousness as John Locke's Essay Concerning Human Understanding (1690). Hardly a book on the subject is written in England from the time of its publication through the Romantic period which does not respond in some way to Locke's text. The text itself is a comprehensive and detailed analysis of the mechanisms of human thought. An analysis which Locke believed had the potential to shed new light on social and religious thought. In the course of the book, Locke himself attempts to use his model to explain many philosophical dilemmas, such as the relationship between the material world, subjectivity and the divine.

The books most sustained influence on British thought was, however, not a result of his philosophizing about these relationships, but rather of his initial impetus to categorize and describe the relationship between various types of human thought. It is the nature of the model of cognition that Locke develops which lead John Stuart Mill, for example, to dub him the unquestioned founder of the analytic philosophy of mind. Many later British thinkers would disagree with Locke, but few would be able to refrain from constructing their own cognitive models as justifications for their social, aesthetic, or religious philosophies in the face of the weight of the Influence of Locke's Essay.

In John Locke's "Essay Concerning Human Understanding", he makes a distinction between the sorts of ideas we can conceive of in the perception of objects. Locke separates these perceptions into primary and secondary qualities. Regardless of any criticism of such a distinction, it is a necessary one in that, without it, perception would be a haphazard affair. To illustrate this, an examination of Locke's definition of primary and secondary qualities is necessary.

Starting from common-sense notions of perception, namely that there must be something in order to perceive something, Locke continues by arguing that ideas in the mind correspond to qualities in the object being perceived. Locke states that:

Whatsoever the mind perceives in itself, or is in the immediate object of perception, thought or understanding, that I call idea; and the power to produce any idea in our mind, I call quality of the subject wherein that power is.

Primary qualities are those aspects of an object that are in and of the object being perceived. Anything that must actually be in an object in order for any object to exist is a primary quality. These, Locke stated, are inseparable from an object. Qualities such as mass, solidity, and extension in three dimensions are all primary qualities. To say that an object has mass and solidity but no shape or extension in three dimensions is inconceivable if not outright ridiculous. So, primary qualities are necessary for an object to be considered an object. If something does not have primary qualities, then it cannot be considered an object but must be considered to be something else.

Secondary qualities, according to Locke, are our interpretation of the effects that primary qualities have on our perceptions and the ideas that come from these perceptions.

such qualities which in truth are nothing in the objects themselves but powers to produce various sensations in us by their primary qualities, i.e. by the bulk, figure, texture and motion of their insensible parts, as colors, sounds, tastes, &c...

Our senses are limited to a certain stratum of perception. We cannot, with our naked eyes, see the workings of atoms, nor the interplay of light particles and atoms in objects in the production of color. However, we can see the results of those interactions, and when light reflects off an object, we can absorb that light with our eyes. Now, when that sense stimulus produces an idea in our minds we interpret it as a colour such as red, green, blue, and so on. This is what Locke meant by secondary qualities.

With this distinction in mind, primary qualities are necessary for an object to be an object while secondary qualities are not. Secondary qualities are contingent upon a perceiver to interpret the sensations produced by primary qualities. Primary qualities are the cause; secondary qualities are the effect.

Nowhere in this essay has the notion of substance or matter been mentioned but it has been assumed. The assumption of the notion of substance in the foregoing distinction of primary and secondary qualities of objects is where George Berkeley's Idealism finds fault with Locke's materialistic account. What Locke assumes substance to be is what cannot be sensed but what must necessarily be, for primary qualities of an object need a substance in which these primary qualities adhere and exist independent of a perceiver. However, the objections to the notion of matter through the criticisms of the distinction between primary and secondary qualities are ill-founded.

In section 41 of Berkeley's "Principles of Human Knowledge" he states that:

If real fire be very different from the idea of fire, so also is the real pain that it occasions very different from the idea of the same pain, and yet nobody will pretend that real pain either is, or can possibly be, in an unperceiving thing, or without the mind any more than its idea.

This passage plays on Locke's distinction between primary and secondary qualities in that the object (fire) through its primary qualities causes the secondary quality (pain) in the perceiver. Berkeley thought that primary qualities causing secondary qualities would be equally true within a world without matter or substance.

However, if there is naught but ideas, and the idea of fire burns a hand by the perception of pain on the part of the perceiver, then where is the separation of the idea of fire within perception and the idea of fire within contemplation? Both happen within the mind of the perceiver yet one produces the real sense of pain while the other does not. In other words, if my perceptions are of ideas and of ideas only, then where is the division in the mind between thought and perception?

There is a very real distinction between thought and perception, a distinction between the perception of being burned by fire and my conception of being burned by fire. So there must be a wedge between thought and perception that drives them apart. Berkeley's Idealism cannot provide such a wedge, as primary qualities have no substance in which they adhere, but in Locke it is substance that can separate perception from thought. There is a two step process at work in which substance is the cause of primary qualities, which cause secondary qualities in the perceiver, and then it is secondary qualities,