John Locke's theory of knowledge included a concept of mind as a mechanism for performing operations on the ideas provided by sensations. But it requires the identification of those ideas in the form of words which stand for those ideas, words which only have a meaning because several people have decided what it is they mean. In order to understand how such a mechanism can emerge over time we need to begin with a basic understanding of the fundamental problem of the interaction between the individual and the external world. Perhaps it would be a little less confusing in terms of modern perceptual psychology. James Gibson suggested an approach to sensation that differed considerably from Locke's, yet helps to clear up some of the ambiguities in Locke's description. Of course Locke's corpuscular theory of sensation has been pretty much outmoded, and because, as he himself admitted, it provides little explanatory power to his theory of knowledge. If we examine the problems under this more contemporary approach what Locke was trying to say might seem clear. J. J. Gibson explained the problem facing the typical observer in these terms.

The observer is immersed, as it were, in a sea of physical energy. It is a flowing sea for it changes and undergoes cycles of change, especially of temperature and illumination. The observer, being an organism, exchanges energy with the environment by respiration, food consumption, and behavior. A very small fraction of this ambient sea of energy constitutes stimulation and provides information. The fraction is small for only the ambient odor entering the nose is effective for smelling, only the train of vibrations impinging on thee eardrums is effective for hearing, and only the ambient light at the entrance pupil of an eye is effective for vision. But this tiny portion of the sea of energy is crucial for survival because it contains information for things at a distance.

Think of this as a selection out of the sea of energy those aspects of the changing array that the physical make-up of the body chooses for its sensations of the outer world. But still, in spite of this selection, the perceiving being is still faced with a great deal of information, more than he can possible process at any one time. Eleanor Gibson explained how this occurs.

In the normal environment there is always more information than the organism is capable of registering. There is a limit to the attentive powers of even the best educated human perceiver. But he is also limited with respect to the complex variables of stimulation by his stage of development and his education.

Modern perceptual psychology, then, recognizes that what one senses in the world around him is not merely a succession of sensual stimuli which the mind must then assemble into diverse things, but, a rich world full of things undergoing change before a background of consistency. In other words, what is constant in the world around us is carried as a background before which we sense changes in the things that are not constant. This explains why we can react to sudden stimuli whose evidence is slim compared to the complexity in the environment. Agreed, that this is a far cry from John Locke, but it does illustrate how his insight was able, only by abstracting from experience, to develop a view of experience well beyond his time. The point I am trying to make is that because of the excessive sensory stimulation in our environment, we deal not with individual sensations but with patterns of sensations. In the words of John Locke, the simple ideas that we form in our mind are always of things. If we accept the Lockean concept that we experience things as simple ideas rather than series of sensations, we then can understand his thoughts on time and succession.

Time and succession are concepts that have posed great problems for philosophers. However, as Locke put it, succession can be seen as a succession of ideas in the mind and time can be seen as the relationship between the succession of ideas and the constant background before which they change. That is why he could understand the subjective nature of time better than others. Seeing ideas as they proceed from the past into the future requires an understanding of the role of memory in everyday action. But it is the insight of John Locke that saw the difference between a length in space and a duration in time as determined entirely through experience that separates him and his successors from the past.

But there is this manifest difference between themThat the ideas of length which we have of expansion are turned every way. and so make figure, and breadth, and thickness; but duration is but as it were the length of one straight line, extended in infinitum, not capable of multiplicity, variation, or figure; but is one common measure of all existence whatsoever, wherein all things, while they exist, equally partake. For this present moment is common to all things that are now in being, and equally comprehends that part of their existence, as much as if they were all but one single being; and we may truly say, they all exist in the same moment of time.

But there is a difference between being and duration for one implies existence and the other continuation of existence. The first ignores time and continuity, the second depends on it. Thus time and duration are inseparable.

Duration and time which is a part of it, is the idea we have of perishing distance, of which no two parts exist together, but follow each other in succession; an expansion is the idea of lasting distance, all whose parts exist together, and are not capable of succession. And therefore, though we cannot conceive of any duration without succession, nor can put together in our thoughts that any being does now exist tomorrow, or possess at once more than the present moment of duration; yet we can conceive the eternal duration of the almighty far different than that of man, or any other finite being. Because man comprehends not in his knowledge or power all past and future things: his thoughts are but of yesterday, and he knows not what tomorrow will bring forth. What is once past he can never recall; and what is yet to come he cannot make present.

...To conclude: expansion and duration do mutually embrace and comprehend each other; every part of space being in every part of duration, and every part of duration in every part of expansion. Such a combination of two distinct ideas is, I suppose, scarce in all that great variety we do or can conceive. and may afford to further speculation.

When a simple animal interacts with the outside world he does not require a mind. The optical senses of a frog are sensitive only to small rapidly moving objects. All of the information needed to snag the fly with his tongue are selected out from the sea of environmental information by the limitations in his visual apparatus. However, the frog also can never sense anything else but small rapidly moving objects, its capabilities are limited by the neural capacities of its simple brain. The concept of mind as a mechanism that extracts from and operates on environmental stimuli as outlined by John Locke provides a clue to understanding how a public language can emerge through communications about private ideas.

Because the individual can name objects which are environmentally common to others ambiguously, names are not assigned to ideas until some kind of consensus is reached. The effect this has is to provide a mechanism other animals lack, that of creativity. Of all of the theories of mind and knowledge only Locke's allows this possible interpretation.

The modern perceptionist view of mind differs considerably from Locke's, but only because the Gibson's had three hundred years of psychological data that Locke lacked. The point I am trying to make is that even considering our twentieth century knowledge, his concept still makes sense. But the major problem, and the major importance of Locke's work was the his explanation of just how it is that all knowledge can be developed entirely from experience. To do this he had to undermine descriptions developed by Scholastics and Rationalists alike. The concept of substance, for example. As you may remember Aristotle made the concept of substance a general term for anything that can be named and talked about. If we begin with this conception of substances, then the way we discriminate between one substance and another is by noting in them what we call accidents. Accidents are not defined as being confined to a substance, thus we can think of snub-nosed without thinking of Socrates. But it is through them that we identify substances. However, if we identify things by accidents, what do the accidents inhere in. Is it material or a substratum, as Aristotle would call it? Is it perhaps substance as a general word for whatever is extended, as Descartes said. This is an age-old scholastic question that Locke attempted to answer through his reliance on experience as the only source of knowledge.

Whatever therefore be the secret abstract nature of substance in general, all the ideas we have of particular distinct sorts of substances are nothing but several combinations of simple ideas, coexisting in such, though unknown, cause of their union, as makes the whole subsist of itself. It is by such combinations of simple ideas, and nothing else, that we represent particular sorts of substances to ourselves; such are the idea we have of their several species in our minds; and such only do we, by their specific names, signify to others, v.g. man, horse, sun, water, iron; upon hearing which words, everyone who understands the language, frames in his mind a combination of those several simple ideas which he has usually observed, or fancied to exist together under that denomination; all which he supposes to rest in and be, as it were, adherent to that common unknown subject, which inheres not in anything else.

As an example of what he means by the unknown subject which inheres not in anything else he cites the story of the Indian who when asked what held up the earth said an elephant and when asked what held the elephant, he said a tortoise. When asked what held up the tortoise, he answered that he didn't know. The problem is that it is not something we can know through experience and therefore it is not something we can know at all. In saying this he was the first to imply that the world might not be dependent on God. I don't mean that he suggested this, it would be entirely out of keeping with his Christian heritage. But it is important that if all knowledge is only of what we can experience then how can we know that God is the beginning of all experience? This is a problem that attracted the Irish Bishop George Berkeley. Can we describe an entirely empirical world known only through experience that was wholly dependent on God for its continued existence?