第58章

SENSATION.

After inner perception, outer perception!

The next three chapters will treat of the processes by which we cognize all times the present world of space and the material things which it contains.

And first, of the process called Sensation.SENSATION AND PERCEPTION DISTINGUISHED.

The words Sensation and Perception do not carry very definitely discriminated meanings in popular speech, and in psychology also their meanings run into each other.Both of them name processes in which we cognize an objective world; both (under normal conditions) need the stimulation of incoming nerves ere they can occur;

Perception always involves Sensation as a portion of itself; and Sensation in turn never takes place in adult life without Perception also being there.

They are therefore names for different cognitive functions, not for different sorts of mental fact.The nearer the object cognized comes to being a simple quality like 'hot,' 'cold,' 'red,' 'noise,' 'pain,' aprehended irrelatively to other things, the more the state mind approaches pure sensation.

The fuller of relations an object is, on the contrary; the more it is something eased, located, measured, compared, assigned to a function, etc., etc.;

the more unreservedly do we call the state mind a perception, and the relatively smaller is the part it which sensation plays.

Sensation, then, so long as we take the analytic point of view, differs from Perception only in the extreme simplicity of its object or content. Its function is that of mere acquaintance with a fact.Perception's function, on the other hand, is knowledge about a fact; and this knowledge admits of numberless degrees of complication.But in both sensation and perception we perceive the fact as an immediately present outboard reality, and this makes them differ from 'thought' and 'conception,' whose objects do not appear present in this immediate physical way.From the physio- logical point of view both sensations and perception differ from 'thoughts' ( in the narrower sense of the word ) in the fact that nerve-currents coming in from the periphery are involved in their production.

In perception these nerve-currents arouse voluminous associative or reproductive processes in the cortex; but when sensation occurs alone, or with a minimum of perception, the accompanying reproductive processes are at a minimum too.

I shall in this chapter discuss some general questions more especially relative to Sensation.In a later chapter perception will take its turn.I shall entirely pass by the classification and natural history of our special I sensations, such matters finding their proper place, and being sufficiently well treated, in all the physiological books.

THE COGNITIVE FUNCTION OF SENSATION

A pure sensation is an abstraction ;

and when we adults talk of our 'sensations' we mean one of two things:

either certain objects, namely simple qualities or attributes like hard, hot, pain ; or else those of our thoughts in which acquaintance with these objects is least combined with knowledge about the relations of them to other things.As we can only think or talk about the relations of objects with which we have acquaintance already, we are forced to postulate a function in our thought whereby we first become aware of the bare immediate natures by which our several objects are distinguished.

This function is sensation.And just as logicians always point out the distinction between substantive terms of discourse and relations found to obtain between them, so psychologists, as a rule, are ready to admit this function, of the vision of the terms or matters meant, as something distinct from the knowledge about them and of their relations inter se.Thought with the former function is sensational, with the latter, intellectual.Our earliest thoughts are almost exclusively sensational.

They merely give us a set of thats , or its , of subjects of discourse, with their relations not brought out.The first time we see light , in Condillac's phrase we are it rather rather than see it.But all our later optical knowledge is about what this experience gives.

And though we were struck blind from that first moment, our scholarship in the subject would lack no essential feature so long as our memory remained.

In training-institutions for the blind they teach the pupils as much about light as in ordinary schools.Reflection, refraction, the spectrum, the ether-theory, etc., are all studied.But the best taught born-blind pupil of such an establishment yet lacks a knowledge which the least instructed seeing baby has.They can never show him what light is in its 'first intention';

and the loss of that sensible knowledge no book-learning can replace.All this is so obvious that we usually find sensation I postulated as an element of experience, even by those philosophers who are least inclined to make much of its importance, or to pay respect to the knowledge which it brings.

But the trouble is that most, if not all, of those who admit it, admit it as a fractional part of the thought, in the old-fashioned atomistic sense which we have so often criticised.

Take the pain called toothache for example.

Again and again we feel it and greet it as the same real item in the universe.

We must therefore, it is supposed, have a distinct pocket for it in our mind into which it and nothing else will fit.This pocket, when filled, is the sensation of toothache; and must be either filled or half-filled whenever and under whatever form toothache is present to our thought, and whether much or little of the rest of the mind be filled at the same time.