(iv) Nevertheless, if Speculative Philosophy remembers its limitations, it is of value to scientists, in its methods, if not in its results. The reason is this. In all the sciences except Psychology we deal with objects and their changes, and leave out of account as far as possible the mind which observes them. In Psychology, on the other hand, we deal with minds and their processes, and leave out of account as far as possible the objects that we get to know by means of them. A man who confines himself to either of these subjects is likely therefore to get a very one-sided view of the world. The pure natural scientist is liable to forget that minds exist, and that if it were not for them he could neither know nor act on physical objects. The pure psychologist is inclined to forget that the main business of minds is to know and act upon objects; that they are most intimately connected with certain portions of matter; and that they have apparently arisen gradually in a world which at one time contained nothing but matter. Materialism is the characteristic speculative philosophy of the pure natural scientist, and subjective idealism that of the pure psychologist. To the scientist subjective idealism seems a fairy tale, and to the psychologist materialism seems sheer lunacy. Both are right in their criticisms, but neither sees the weakness of his own position. The truth is that both these doctrines commit the fallacy of over-simplification; and we can hardly avoid falling into some form of this unless at some time we make a resolute attempt to think synoptically of all the facts. Our results may be trivial; but the process will at least remind us of the extreme complexity of the world, and teach us to reject any cheap and easy philosophical theory, such as popular materialism or popular theology.*

Before ending this chapter I will say a word about the three sciences which are commonly thought to be

Theology, whether "natural" or "revealed," is a form of Speculative Philosophy, in our sense of the word. So, too, is Atheism.

specially philosophical. These are Logic, Ethics, and Psychology. Logic simply is the most fundamental part of Critical Philosophy. It deals with such concepts as truth, implication, probability, class, etc. In fact it may be defined as the science which deals with propositional forms, their parts, their qualities, and their relations. Its business is to analyse and classify forms, and to consider the formal relations that can subsist between them. Now all science consists of definite propositions, and each of these is of one of the forms which Logic studies; but it is not the business of any other science explicitly to discuss propositional forms. Similarly all science is full of inferences, good and bad, and all inference depends on relations that are supposed to subsist between premises and conclusion. But it is for Logic, and for it alone, to decide what relations do in fact justify inference, and whether these relations do actually subsist in a given case. Thus Logic is that part of Critical Philosophy which deals with the most. general and pervasive of all concepts, and with those fundamental beliefs which form the "connective tissue" of all knowledge.

The greater part of Ethics again is simply a branch of Critical Philosophy. It is a fact that we not only believe that such and such events happen, but that we also pass judgments of approval or disapproval on certain of them. Such judgments use peculiar concepts, like good and bad, right and wrong, duty, etc. A very important part of Ethics is the attempt to analyse and define these peculiarly obscure notions which we all use so gaily in everyday life. Again, there are a great many judgments of value which many people assume as certain; e.g. Pleasure is good, It is wrong to tell lies, A man has a right to do what he likes with his own, and so on. Another important part of Ethics is the attempt to state such judgments clearly, and then to see what evidence, if any, there is for them. Thus, Ethics is that part of Critical

Philosophy which analyses the concepts and criticises the presuppositions that we use in our judgments of approval and disapproval.

Psychology, as it seems to me, is not a part of Philosophy at all, but is simply one of the special sciences. This is shown by the fact that, unlike Logic and Ethics, it argues inductively from experiment and observation, though the observation takes the peculiar form of introspection. It is, however, a very peculiar kind of special science. It is obvious that Chemistry and Physics are much more like each other than either of them is like Psychology. The reason is that the two former sciences treat two rather different but very pervasive sets of material properties, whilst the latter deals with minds, which apparently occupy a unique and strangely isolated position in the Universe. Or, again, we may say that Psychology deals with what is relatively private, whilst all the other natural sciences deal with what is relatively public. If, now it should be asked why Psychology has been supposed to be specially connected with Philosophy, I think that the following answers will be fairly satisfactory.

(i) Psychology supplies Critical Philosophy with a number of concepts as raw material for analysis and criticism. Such are the concepts of mind, self, consciousness, instinct, sensation, perception, etc. Now these notions we all admit to be highly confused and obscure, whereas we are inclined to think-until we learn better— that there is no particular difficulty about such concepts as place, date, matter, cause, etc., which we use in the other sciences. Thus a great part of any standard book on Psychology does in fact consist of attempts to analyse and define certain concepts, and this is of course Critical Philosophy.

(ii) When we try to clear up the meanings of physical concepts like place, date, matter, etc., we often find that a reference to the processes by which they come to be known is essential, and that they owe part

of their obscurity to the abstractions which science and common-sense have made. Thus, in doing Critical Philosophy, we do constantly have to appeal to facts which belong to Psychology, even when we are not primarily dealing with psychological concepts.*

(iii) In Speculative Philosophy we ought, no doubt, to take into account the results of all the sciences. But, owing to the unique subject-matter of Psychology, we shall go hopelessly wrong if we omit it, whilst we shall not go so hopelessly wrong if we omit one of the sciences of matter, such as Mineralogy or Botany.

For these reasons we may admit that Psychology is of peculiar importance to Philosophy, though we must deny that it is a part of Philosophy, like Logic and Ethics.

It

The present book deals wholly with Critical Philosophy, and only with a small part of that. It is concerned almost entirely with an attempt to clear up some of the concepts used in the natural sciences. does not deal even with all these, e.g. very little is said about causation. The reason is that I did not want to deal with purely logical questions; and it is hardly possible to discuss causation adequately without going into the question of induction, in which causation is commonly thought to play an important part.

Additional works that may be consulted with profit :
F. H. BRADLEY, Appearance and Reality, Introduction.
H. SIDGWICK, Philosophy: its Scope and Relations.

B. A. W. RUSSELL, Our Knowledge of the External World,
Lectures I and II.

J. GROTE, Exploratio Philosophica, Part I. Caps. I. and II.
DESCARTES, Rules for the Direction of the Mind.

It is also true that we cannot give a complete treatment of Logic (especially the subjects of Inference and Probability) without referring to minds and their special limitations.

C

CHAPTER I

"When I use a word," Humpty-Dumpty said in rather a scornful tone, "it means just what I choose it to mean -neither more nor less."

"The question is," said Alice, "whether you can make words mean so many different things."

"The question is," said Humpty-Dumpty,

be Master-that's all.”

which is to

(Lewis CarroLL, Through the Looking-Glass.)

The Traditional Conception of Space, and the Principle of Extensive Abstraction

It is not ultimately possible to treat Space, Time, and Matter, as used in physical science, in isolation from each other; for we shall see that they are closely bound together in their very natures. This is, however, a comparatively recent discovery; and the traditional view, with which most of us still work in daily life, is that Space and Time, at any rate, can be adequately analysed in isolation from each other and from matter. As this is the familiar view, it seems best to start from it and gradually to point out and remove its imperfections. In any case we must start somewhere; and the fact that the three concepts in question have so long been treated as separable without serious practical error shows that, to a great extent, they are separable. The truth is that what is logically most primitive in nature is not what is now most familiar to us, and therefore it is better for didactic purposes to start with the logically derivative but practically familiar, and work back to the logically primitive but practically unfamiliar. For example, the immediate data of sense, like coloured patches, are logically prior to the notion of physical objects, which