In the same year, 1936, as his essay on ‘Comparative Method’¹ appeared, Rupert Lodge set out what he took to be the three types of thought in The Questioning Mind: a survey of philosophical tendencies.²

[79] in every kind of knowledge (…) two sharply distinct tendencies have made their appearance. The first, the tendency toward caution, toward factuality, toward faith in direct sensation and intuition, and away from everything smacking of ‘interpretation’, of the construction of mental sky-scrapers, is known, in the history of philosophy, sometimes as empiricism, but more frequently as realism. In its simpler and more naive forms, it looks upon reality as something like a child’s box of blocks. With these, children construct whatever edifices please their fancy. But, when their play is over, the nurse puts them all back again into their box, and there they are, what [80] indeed they always were, separate individual blocks, and nothing more. So David Hume, who represents the culmination of the tendency associated with the name of John Locke, reduces the reality sought in experience, to a number of quasi-atomic ‘simple ideas’.  Like the child’s blocks, these are, for Hume, essentially separate. We can put them together, if we will: we can ‘associate’ them in our fancy, at our pleasure. But, when our imaginative play is over, along comes the relentless metaphysician and sweeps them up, and puts them back again into their box, ‘conjoined, but not connected’. Bertrand Russell, at the present day, declares that there are only two possible attitudes toward Hume’s arguments : to accept them, or to ignore them. Neo-realist logic applies to all philosophies the stern test of analysis into separate, hard-and-fast concepts, which may be related only in certain specified ways ; much as the child’s blocks can be juxtaposed only in the three spatial dimensions, in front or behind, above or below, to right or left. It must be admitted that realism, with its insistence upon caution and exactitude, represents one of the fundamental tendencies in philosophy, a tendency strong and active in us all.

The second tendency, toward interpretation, logical expansion, and the inferential construction of progressive systems which, in proportion as they become broader and deeper, throw more and more light upon the objective content of experience, is known, in the history of philosophy, sometimes as rationalism, but more frequently as idealism. Undoubtedly persuasive in so far as it remains reasonably close to the experiences which it is endeavouring to interpret, idealism tends to [81] withdraw from its starting-points and to enter wholly into a mental realm which is, perhaps, excessively transcendental. Idealists often feel more at home with the absolute ideal of an ultimate system, than with the men and women among whom they live. It must be admitted that they frequently withdraw from the detailed perplexities which seem to be part and parcel of our actual, day-to-day living, into a world of the imagination, where all seems bright and fair, and from which conflicts and inconsistencies, doubts and fears, are excluded with the unyielding rigidity of court etiquette.

In opposition to this tendency to concede almost divine rights to absolute systems, there has arisen a third philosophical tendency, known as pragmatism. Pragmatists avoid absolute systems as they would the devil. They keep close to the biological and social, stimulus-reaction world, in which humanity finds itself, willy-nilly. They substitute the development of efficiency in solving practical problems, for such remote and unprofitable ideals as the quest for ultimate truth. These three tendencies, realist, idealist, and pragmatist, all have a strong appeal; and with them in mind, we shall proceed to answer the questions with which we started, namely, the questions as to the origin, function, validity, and limitations, of what would ordinarily be called ‘knowledge’.

The origin of knowledge, for realists as for idealists, is what we feel to be the essential objectivity of experience. It is by trying to understand what is there to be understood, that we originate knowledge. From the realist standpoint, what enables us to understand is analysis, followed by synthesis. We divide experience, [82] if we are realists, into elements so small and so simple that we directly apprehend their true nature. This we do both in respect of content, analysing until we reach the simple sensory qualities, red, green, blue, etc., and in respect of form, analysing until we reach the ones of formal arithmetic and the elementary class-concepts of formal logic. These ultimate units once attained, we proceed to build up, step by step, complex structures and tissues of relations which ‘correspond to’ the realities which form the content of our experience. These analytic-synthetic structures, which we thoroughly understand because we have ourselves constructed them out of known elements, are used as patterns by which to understand the world in which we live. The ability of the bulrush to withstand strains is explained in terms of the engineering principle of trusses, and the mechanism in the human ear is explained in terms of the grand piano or the telephone.

From the idealist standpoint, on the other hand, what enables us to understand is synthesis, followed by analysis. The patterns by reference to which we classify our experiences represent for us, if we are idealists, not complex structures built up out of known elements, but the concentrated essence of far-reaching systems of belief. We understand a bulrush as a specific case of the whole system of botanical knowledge, and the auditory mechanism of the human ear as a specific case of a vast system of neurological knowledge. The idealist, that is to say, bases his faith, not upon any direct acquaintance with supposedly simple ideas, but rather upon the ideal of the systematic unity of knowledge. In the light of his conception of an ideal system, [83] he reformulates his first hypotheses, and transforms them into something more nearly approaching a final formulation, in which they would become organic portions of ultimate truth.

Finally, from the pragmatist standpoint, there is no such thing as the ‘knowledge’ possessed by realists and aspired to by idealists. There are only varying degrees of efficiency in solving, by appropriate reactions, the problems set us, here and now, by biological and social stimuli. The ‘origin’ of such reaction-processes is the stimulus; and while the systems constructed by science may prove useful in assisting toward efficient reactions, these systems merely provide a longer circuit of technical reaction, in place of the shorter circuit of instinctive response. The longer circuit is not employed because it is ‘truer’, but simply because, in the complex conditions of modern life, it is more efficient. Statistical methods are almost always more efficient than guesswork.

The function of knowledge, for both realist and idealist, is to enable us to know, to understand reality, primarily for the sake of knowing, and only secondarily for the sake of practical advantages. Both schools believe that the practical advantages only come if we persist in treating them as strictly secondary: if, like Pasteur or Madame Curie, we concentrate wholeheartedly upon the theoretical problem of discovering what the objective, factual side of experience really is, in itself. For pragmatists, on the contrary, such an ideal is remote and unattainable; it is formulated without due regard to the conditions of human life, and is to be set on one side as a mistake. To know ‘for the sake of knowing’ seems, to a pragmatist, a vicious abstraction. [84] We should acquire what is called ‘scientific knowledge’ — which is a tissue of essentially practical solutions of problems fundamentally practical, of biological and social significance — not ‘for knowing’s sake’, but for its practical values, ‘for the praise it gets, the gain it brings, the love it breeds’, as Browning puts it, as well as for its sheer efficiency. The advertisements of libraries of literary and scientific ‘classics’, which depict the prudent purchaser as the happy centre of a social gathering, attracting by his literature and his wit all whom he desires to attract, illustrate this idea of the function of knowledge, namely: success.

The validity of knowledge, for realists and idealists, depends upon its objective value. For the realist, this objectivity is a matter of direct apprehension, after a process of analysis. For the idealist, it is an ideal toward which, by the progressive construction of hypotheses representing the concentration of ever wider systems of beliefs, we gradually advance. For the pragmatist, the test of validity is success in solving the immediate problem, a success understood in a practical, and not in a theoretical, sense.

The limitations of knowledge present difficulty to our attempt at a brief statement. Realists tend to recognize no theoretical limits to knowledge. We cannot, they urge, tell beforehand what we shall be able to discover, and what not. Once we have analysed down to simple ideas, and can proceed to construction, there seems to be no place where we can draw a line and say: ‘Thus far and no further.’ The future of knowledge is a future in which only advance, unlimited possibility of progress, can be predicated, provided that strict [85] adherence to cautious methods is observed. Idealists, on the other hand, once they have constructed the outlines of their absolute system, have great difficulty with the ‘subject-object’ relation. Knowledge for them is always knowledge-for-a-knower, never just knowledge-in-itself. The knower constitutes a definite limitation upon knowledge.³ If we regard knowledge as a picture, it is a picture which requires a spectator. The knower is always the spectator, and can never fit himself into the picture; and yet, with him left out of the picture, the picture can hardly be true to the whole of experience. This fundamental dualism, this splitting up of experience into a subject and an object, which have no meaning apart from one another, and yet resist complete unification,⁴ remains a serious difficulty for idealists. Pragmatists, however, regarding the idea which idealists set before themselves as a vicious abstraction, a self-made puzzle to which no solution is theoretically possible, confine themselves to the successful solution of practical problems piecemeal, and can see none but practical and temporary and accidental limitations to the efficient solution of all genuine problems which may arise.

In final summary, it may be stated that realists believe in knowledge as a fact, idealists only as an ideal goal toward which they aspire. Pragmatists regard it as a mischievously misleading notion, in whose place they prefer to set a practical ideal: the ideal of efficient, practical solution of particular, essentially non-systematic problems, which are set by the biological and social stimuli which constitute the concrete environment of humanity as we find it.