Simple Ideas and Modes

Although simple ideas carry with them a presupposition of real existence, Locke held, the names of simple ideas signify both the real and the nominal essences of the qualities they represent. [Essay III iv 2-3] Like the simple ideas themselves, which are involuntarily received in perception, the names of simple ideas have non-arbitrary content.

We find it difficult (and, usually, unnecessary) to classify them into sorts, and when we do so-as, for example, with colors or sounds-it is typically by reference to their perceptual origins rather than any supposed ideational similarity. [Essay III iv 16-17] Similarly, because each simple idea is a uniform perception, easily retained and intended to conform only to itself as an archetype, our names for simple ideas are rarely vulnerable to imperfection; the more simple the idea, the less likely we are to misuse the word that expresses it. [Essay III ix 18-19]

One consequence of all this is that the names of simple ideas are indefinable. At peril of an infinite regress, the provision of verbal definitions must ground out on some indefinable terms, and since simple ideas have no component parts that could be assembled under the direction of an appropriate definition, their names are perfectly suited to that role.

Scholastic efforts to offer definition of such simple ideas as motion or light, Locke argued, are ludicrous precisely because they so patently fail to produce any new idea in the minds of those who hear them. Imagine the comparable folly of trying to provide auditory definitions of visual ideas, or vice versa. [Essay III iv 4-11]

The names of mixed modes, on the other hand, are general terms that signify abstract ideas governing species of human actions. These names clearly are definable, since it is always possible in principle to offer a comprehensive list of those simple ideas which, assembled together by the mind, would constitute the appropriate complex idea.

That's why we don't need to witness an act of sacrilege or experience the resurrection of the dead in order to understand what kind of events those terms would signify. [Essay III v 1-5] Thus, Locke supposed that the initial formation of the abstract idea (and the stipulation of the name associated with this mixed mode) can be freely performed without any possibility of error.

It is only the subsequent use of the same word by other members of the same language-community that become vulnerable to mistake because they may fail to associate the word with the already-intended idea. [Essay III vi 43-45]

Here, even more obviously than in the case of substances, our acts of naming and classification are purely arbitrary, lacking any natural foundation. We do not discover the categories of human action (or their moral significance) as existing patterns of the natural world, but rather invent them in accordance with our own decisions about how to pursue practical life amongst one another. [Essay III v 6-9]

The vocabularies of morality, religion, and law are entirely of our own devising. This renders the use of such terms less problematic, Locke noted, and makes their misuse and confusion even less excusable.

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Human Knowledge

Having explained the origin of our ideas and the use of words to signify them, Locke was prepared to consider the nature of human knowledge. He began with a simple definition: Knowledge then seems to me to be nothing but the perception of the connexion and agreement, or disagreement and repugnancy of any of our Ideas. In this alone it consists. [Essay IV i 2]

This definition gives rise to an obvious objection: if all human knowledge were wholly concerned with ideas, then it would lack an adequate foundation in reality and there would be no difference between the wise contemplation of philosophers and the fanciful but coherent imagination of the insane. Locke's response was two-fold: with respect to general knowledge, he boldly defended its detachment from anything other than our ideas, but with respect to knowledge of particulars he tried to show that there is a legitimate cognitive state that "goes a little farther than bare Imagination." [Essay IV iv 1-2]

Actual knowledge occurs only when we are actually perceiving the agreement in question, Locke supposed; our inclination to assent to what we've known in the past but are not presently attending to he called habitual knowledge. This capacity is clearly important for the development of learning generally; we can't focus on everything at once,

and it makes sense to rely upon our memories for general truths we have mastered on some occasion in the past. [Essay IV i 8-9] Thus, it makes sense to say that I know (habitually) the multiplication tables even at moments when I'm thinking about other things, provided that I can, upon challenge, call to mind the product of 8 and 7. The more crucial issue about human knowledge is to explain how it occurs in the first place.

No Knowledge is Innate

One account Locke unambiguously rejected from the outset is the supposition that human knowledge is innately inscribed. Noting the remarkably wide-spread agreement of individual human beings in their acceptance of both speculative and practical principles, the innatist argues that universal consent implies an innate origin.

Locke's response was two-fold: He denied the supposed fact of universal consent, supposing this to demonstrate the falsity of the innatist view. What is more, Locke argued that if there were any genuine instances of universal consent, they would more naturally be explained by universal possession of an intellectual faculty or by acquisition through some universal experience. [Essay I ii 1-2]

Granting that if general truths about logic were innately know by all human beings, then they must also be universally accepted, Locke emphatically denied the consequent. If the innatists were correct, then children (and mental defectives) would be the most pure and reliable guides to logical truth; but they are not. [Essay I ii 24-27] Of course the innatist reply to such counter-examples is to suppose that assent to innately inscribed principles is delayed until each individual is able to employ the faculty of reasoning.

But why should this be? Either reason is necessary for the discovery of such principles, in which case they are not innately known, Locke argued, or else reason and logic are merely coincidental features of human development, in which case both seem frivolous. [Essay I ii 6-13] Surely, in fact, the use of reason is properly concerned with our assent to general truths.

Locke agreed with the innatists that there is a significant distinction between truths to which we assent immediately upon first framing them on the one hand and, on the other hand, truths that require our careful consideration. But this distinction between self-evident and acquired knowledge, he supposed, doesn't correspond to the innatist identification of the most fundamental truths.

We assent to specific instances at an earlier stage of development than to speculative maxims themselves, and this is most easily explained by the fact that we acquire the particular ideas involved in the former long before we have manufactured the abstract ideas required for the latter. [Essay I ii 14-19] Careful attention to the development of knowledge in individual cases clearly shows it to involve the gradual acquisition of the requisite ideas, perception of whose agreement or disagreement constitutes knowing in each instance.

Achieving Certainty

Locke's definition of knowledge as perception of the agreement (or disagreement) of ideas clearly indicates two fundamental criteria for acquiring knowledge: first, we have to have the requisite ideas, then we also have to perceive the connection between them. Failure on either of these counts will leave us short of the certainty characteristic of genuine knowlege. [Essay IV iii 1-2]

The extended genetic account of our ideas in Book II of the Essay was designed to assist in satisfaction of the first criterion, by helping us to acquire a suitable stock of clear and distinct ideas about many things. But even where our ideas are amply clear, we may fail to achieve certain knowledge if we are unable to recognize the ways in which they are related to each other. [Essay IV ii 15]

Consider, for example, how the two criteria apply to specific areas of possible human awareness: Our passive reception of simple ideas from external objects provides only practical assurance of the existence of the objects themselves, so our knowledge of material qualities and substances is always limited in certainty.

But non-substantial complex ideas refer to nothing outside themselves, so any connections we perceive among them are "infallibly certain." For this reason, as we'll see later, Locke held that all mathematical and moral reasoning is characterized by perfect certainty. [Essay IV iv 4-8]

What Locke's definition clearly demands is that all knowledge is relational in structure, or propositional in form; it invariably involves "the joining or separating of Signs, as the Things signified by them, do agree or disagree with one another." [Essay IV v 2] But since both ideas and words are properly understood as signs, Locke believed it vital in principle, though often difficult in practice, to distinguish between truth in thought and truth in language.

Ultimately he distinguished between mental propositions in which ideas are perceived to agree and verbal propositions that affirm the agreement of words. In both cases, the criterion of truth is that the relation of the signs conforms to a more fundamental agreement that holds among the things they signify. [Essay IV v 3-5] Naturally the two kinds of proposition are connected with each other.

Certainty about the truth of a verbal proposition requires that it accurately express the agreement of the ideas signified by its terms; certainty about the knowledge itself further requires that we actually perceive that agreement among ideas. [Essay IV vi 3]