which are relevant to the purpose of the particular inquiry, ignoring those other features which lie outside its scope. So Physics ignores beauty and emotion in its effort to describe the relations of natural entities in mechanical terms. This is a legitimate and very necessary process, but it inevitably necessitates that the Truth of Science is relative only. The price which Science pays for its precision and exactness is the relativity of the truth at which it arrives.

The chapters in the book which deal with the development of Mathematics and Science, and in particular with the physical theory of relativity, are there simply as showing how the general theory of relativity is illustrated in this particular case. Dr Whitehead's books, 'An Enquiry concerning the Principles of Natural Knowledge' and 'The Concept of Nature,' have clearly influenced Lord Haldane very much in his treatment of this subject; and he pays a warm tribute to the value and originality of Dr Whitehead's investigations. Dr Whitehead has protested against what he calls the bifurcation of nature into nature apprehended in awareness and nature which is the cause of awareness, or into nature as the play of molecules and radiant energy and nature as presented with psychic addition such as colour and smell to mind. To drag in mind in this way is, as he points out, shirking the problem of Science, which is to describe the relations inter se of things known abstracted from the bare fact that they are known. The bifurcation theory is acceptable for the simplicity it introduces, but, if accepted, it is a confession of failure on the part of Science. Lord Haldane points out that, if Dr Whitehead pushes his theory a little further, the logical result it that the distinction between mind and nature vanishes, and nature for Dr Whitehead becomes Knowledge in the wide sense in which our author uses the term. Meaning, interpretation, significance all these things fall within Dr Whitehead's world of Nature. As Lord Haldane says:

"The portal of Nature was to be bolted and barred against mind, but mind has apparently gone round the corner, got in by a back-door and taken possession of the building. Events," "recognition," "objects"! Here we have Knowledge with all its implications, and Knowledge in which the

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"significance" which for Prof. Whitehead is the reality of our experience of nature consists. I am far from complaining; I am in agreement with the author. But I feel I have been led by him into territory which seems not new but somewhat familiar to me. If we went a little further we might expect, and not without reason, to find that the boundary line between mind and nature and the entire distinction between them fell within Knowledge as having been established only by reflexion.'

An interesting description follows, showing how Dr Whitehead arrives at the Einstein Theory of Relativity, but from more fundamental premises than those from which Einstein starts. The real philosophical value of the physical Theory of Relativity, which Lord Haldane describes at some length, lies in this, that in the theory we have a very exact and definite application of the broader principle which our author is maintaining. Space and time, the very structure of the universe, are shown in themselves not to be absolute, but to be the relative forms in which experience is made manifest. Once the relativity of these apparently absolute characteristics is grasped, the relativity of other branches of Knowledge appears less strange.

But the most important feature of the whole theory of Relativity is that it exhibits our knowledge of Nature as the union of subject and object or of mind and externality. Space and Time for the relativist are but the varying differentiations of the ultimate space-time manifold, which in itself is a pure concept or universal. The objective form of Space and Time which this assumes is relative only and existent for Knowledge alone. Thus, unless we are to bifurcate Nature and say the space-time manifold is the cause of our awareness, and that Space and Time are but psychic additions to the real causal Nature, we must admit that significance and meaning cannot be separated from Nature, whereupon Nature assumes the form of that within which 'mind' and 'object' fall, and is simply an aspect of what Lord Haldane calls Knowledge.

Prof. Eddington,* as Lord Haldane shows, goes much further than this, and takes up the rather extreme

See his article on Einstein in the 'Q. R.' (No. 462) for January 1920.

I subjective attitude that the external world is comIparatively unimportant, and that the importance of mind in producing the so-called laws of Nature is far greater than realised. Prof. Eddington uses the words, It is the mind which, by insisting on regarding only the things that are permanent, has actually imposed these laws on an indifferent world. . . . The structure cannot be built up without material; but the nature of the material is of no importance.'

Prof. Eddington's views may lead him to a position not very different from that of Dr Whitehead, but it is unlikely that the latter would accept this position where, by treating mind as a thing, Prof. Eddington is reintroducing the bifurcation doctrine. Finally Lord Haldane says:

'However, therefore, we look at it, the theory of relativity in physical measurement means this, that our measurements are what they are because of concepts through which knowledge effects them. . . . It is through general principles, and not by immediate awareness in its simplicity, that we get our knowledge of physical nature; and the reality we discover is of an order in character the same as that of our knowledge about it.'

This is the basis of the doctrine of degrees of knowledge, truth and reality. What is actual discloses a variety of aspects. The description of each aspect gives knowledge only of that level or degree to which the aspect belongs, and the standard of truth for this level of knowledge is therefore only a relative standard.

It is scarcely possible to do more than refer to the many applications of the complete principle of relativity which Lord Haldane gives in considering other problems in other branches of knowledge. For instance, we find an application in his treatment of individuality. Finite personality is relative. It is not an absolute fact or an ultimate state. My friend, John Smith, is not merely an object of my experience. I have a deeper knowledge of John Smith than that of objective existence. He finds union with my personality in so far as both our personalities are relative to a greater whole. It is this common source or identity in difference in our modes

of thinking in which we find the link that makes John Smith more than an objective fact; and my friend John Smith appears to me as possessing shape and weight and colour and all the characteristics of a human body, only at a certain stage in knowledge. At a further stage in knowledge which includes and transcends the first, he is there as my friend. But it is impossible to do justice to such a wide theme in a few sentences.

At a later stage in the book Lord Haldane applies this to problems of political science. The question, for instance, of whether or not such a thing as a General Will exists is a question which need trouble us very little if we realise that what is meant by General Will is just the common aim and purpose which evolves itself from the people and which rests on this identity in difference, on the fact that individuals are not mutually exclusive. True individualism is not to be found except where a man lives the social or group life. This identity of purpose is, as Lord Haldane points out, the ultimate basis on which sovereignty rests. Moreover the progress in conception from human beings as mechanisms and then as living organisms and finally as personalities is an example of the different levels at which Knowledge manifests itself.

Lord Haldane's treatment of the New Realism is of great interest. He exhibits it as the reaction against extreme forms of subjective idealism, which reaction takes the shape of the projection of universals into the non-mental world and a strenuous assertion that what is known is strictly non-mental and independent of the act of knowing. He values this reaction as bringing strength and vitality to philosophical research, and believes it to be but an oscillation in the general progress of philosophical thought. 'Progress takes place by oscillation succeeding oscillation and reaction following on reaction.'

But perhaps the most interesting chapters on the history of philosophy are those which trace the development from Berkeley and Hume through Kant after which we reach the parting of the ways, the one way giving the development from Kant through Schopenhauer and Bergson, while the other gives the development through Hegel and the modern school of Hegelian

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thought. The importance of Kant's work can scarcely be over-emphasised; and yet Kant, not being in bitter earnest with the doctrine that Knowledge is foundational, did not push his work to its conclusion. Questions of the nature of the raw material of feeling and of the 'thing in itself' remained open for him. The fact remains, however, that he changed the whole course of philosophical thought. Schopenhauer, looking further afield, concentrated on the will as the 'key to the nature of every phenomenon in Nature,' instead of pushing the doctrine of Knowledge to its conclusion. Will, for Schopenhauer, became a sort of thing in itself.' Bergson has followed much the same line, concentrating on Intuition. It remained for Hegel, pursuing the other line, to work out the doctrine of Knowledge in its fulness. No doubt his system suffers from too great rigidity. He attempted to demonstrate the relations of the stages of the real in too cut-and-dry a fashion. But, for all that, the essence of the doctrine of Knowledge is to be seen in Hegel's works in his conception of the Idea realising itself in mind.

'Such, as I understand it, is the Hegelian view of the relation of the cosmos to the completed entirety of Knowledge, the Idea realising itself in mind with the combination of the general and particular moments in its activity. The factors in that activity are the abstractions of universal and particular. The actual is always concrete and is self-developing experience.'

The influence of Aristotle on Hegel was very great, and the essentials of the doctrine of Knowledge are to be found in the works of Aristotle. Whether we accept the conclusions of Hegel or not, he has given us the method; and this is the, really important feature of his work.

Without rewriting the book it is impossible to follow Lord Haldane further in his chapters on the relation of the Individual to the State and of Man to God, and all the other principal applications of the degrees of knowledge which he gives. In conclusion we would say that, though the book is far from easy, it will repay any who have the patience and take the trouble to read it diligently. It may be that Lord Haldane is