There has always been a certain indefiniteness about the nature of the distinctions between the different types of philosophical theory and correspondingly about the meaning of each particular “-ism”. It is obviously not an easy matter to describe a whole outlook; an attitude of mind which is felt to cover a wide range of problems cannot readily be communicated without going over all these problems. Thus it is that philosophers who disagree never seem to come to an end of their disagreements, and can hardly even understand one another. But if anything could alleviate such misunderstandings, it would be a resolute attempt to define exactly the issue or issues between different views; and this is a task which is all too seldom undertaken. It is recognised that there is a natural opposition between rationalism and empiricism, but the basis of the opposition commonly remains obscure or is wrongly stated. In briefly discussing the issue and defending empiricism I cannot hope to show exactly how this theory should be distinguished from those which go by the name of realism, naturalism, materialism, pluralism, determinism and positivism. These are all, I should argue, connected with empiricism; it is on an empiricist view, and only so, that they can be maintained. But I take empiricism as central, as giving the best general description of the philosophy which the other terms partially convey, because the issue which it raises and which it disputes with rationalism, is fundamental to logic, being concerned with truth itself. In the discussion of this issue the ways in which more detailed issues should be dealt with, will in some degree appear.

Rationalistic theories of all sorts are distinguished from empiricism by the contention that there are different kinds or degrees of truth and reality. The distinguishing-mark of empiricism as a philosophy is that it denies this, that it maintains that there is only one way of being. The issue has been confused in the past by a reference to knowledge. It was quite naturally maintained, by those who postulated different ways of being, that in relation to them different ways of knowing are required. Hence empiricism has been connected, in the history of philosophy, with the view that there is only one way of knowing, and particularly that that way is what was called “sense” in contrast to “reason”; or, rather differently, that sense is the only originator of knowledge. But

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fundamentally the issue is logical; the dispute is about ways of being or of truth, not about ways of knowing truths. It is only after it has been assumed that there are other truths than matters of fact, or that there are objects which “transcend” existence, that a special faculty has to be invented to know them.

Thus, although we naturally associate rationalism with the theory of a mental faculty of reason, the discussion of faculties will become pointless if it can be shown that any postulation of different orders of being is illogical. The same criticism will serve whether the differences are said to be of kind or of degree, since the differences of degree are to be determined in relation to a supposed highest degree, which is that of a supremely real object or Absolute. It is because objects of “higher reality” are supposed to transcend experience that the opposition to transcendentalism has the name empiricism. But if experience (by which, of course, is to be understood not our having experiences but what we experience) consists of matters of fact, then it enjoins us to reject all ideals or powers or whatever else may be contrasted with facts. Moreover, rationalistic views are contrary to experience, not merely because they set up something additional to facts, but because they set it above facts, because they make it appear that facts are somehow defective, that they are not real enough in themselves but require to be supplemented by explanations, ends or whatnot, before they can be understood or accepted by a mind.

The chief, and I think final, objection to any theory of higher and lower, or complete and incomplete, truth is that it is contrary to the very nature and possibility of discourse; that it is “unspeakable”. The empiricist, like Socrates, adopts the attitude of considering things in terms of what can be said about them, i.e., in propositions.note And he regards this not as a “second-best”, but as the only method of speaking or thinking at all, since every statement that we make, every belief that we hold, is a proposition. Since, then, the supposed higher and lower objects of experience both take the propositional form, we are concerned with a single way of being; that, namely, which is conveyed when we say that a proposition is true. Deviation from this view must take the form of saying either that facts are propositional but ideal explanations are above the propositional form, or that explanations are propositional and what they have to explain are mere data, not yet propositionalised. But in order to indicate data or ideals, we have to make statements. If there were anything either above or below the proposition, it would be beyond speech or understanding. If, for example, there were anything that required explanation before it became intelligible, we could say nothing about it in its unintelligible form; plainly, then, we could not even say that it had such a form. And, in general, it cannot be maintained either that the proposition is our way of understanding things which in themselves are not propositional, or that we have further ways of understanding the proposition which is in itself defective. Whatever

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“explanation” may be, it must at least be a relation of such a sort that what is explained and what explains it can both be stated and believed, i.e., are both propositions. But if there is no way of getting behind the proposition to something either lower or higher, we must assume that propositions can stand by themselves with nothing to supplement them, that facts need no explanation. Discourse, in fact, depends on the possibility of making separate statements, in regard to each of which the very same question can be asked — “Is it true?”

It follows that the conception of higher truths than those of fact, and that of a total truth to which all “merely particular” truths contribute, have both to be rejected. The latter view is what is currently called idealism, but since it differs from the former only in holding that there is a highest truth instead of a number of higher truths, it can be regarded as a variety of rationalism. The objection to rationalism is just that what is meant by “truth” is what is conveyed in the proposition by the copula “is”. And logically there can be no alternative to “being” and “not being”; propositions can only be true or false. There is no question, therefore, of degrees or kinds of truth; of higher and lower orders of discourse, dealing, e.g., respectively with realities and appearances. The very theory that attempts to make such a distinction has to be put forward in the form common to all discourse, it has to lay claim to the “being” signified by the copula, it has to face the direct question, “Is it true?” Thus empiricism regards it as illogical to make such distinctions as that between existence and subsistence, or between the “is” of identity, that of predication and that of membership of a class; and still more obviously illogical to say that there is something defective about “is” itself. These are all attempts to get behind the proposition, to maintain — in words! — that we mean more than we can say.

Considering propositions as they occur in discourse, we find that they can be asserted or denied, questioned, proved or disproved. In saying, then, that whatever can be asserted can be significantly denied, i.e., that there are no undeniable truths, and that whatever can be asserted or taken for granted can also be made a subject for inquiry, can be questioned or proved, i.e., that there are no unprovables, we are conveying certain characters of the common “is” of discourse (certain conditions of existence). In particular, there is no question of its indicating “necessity” as something over and above actuality. As related to other propositions any proposition has what we may, if we like, call “contingency”; but at the same time, as distinct from other propositions, as being a proposition and therefore requiring separate statement, any proposition has “absoluteness”. The forms of assertion, denial and implication being precisely the same in relation to the supposed different kinds of “is”, there is no way of establishing the difference. We can say that certain truths are of the peculiar “necessary” sort, just as we can say that no truths are “absolute”, but in both cases our speech bewrayeth us.

Rejecting in this way the distinction between necessary and other

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truths, empiricism takes up the position that in discussion or inquiry any proposition can be treated as (a) a conclusion to be proved from premises accepted, (b) a premise accepted to be used in proving some conclusion, (c) a hypothesis to be tested by the observation of the truth or falsity of the conclusions drawn from it, or (d) an observation to be used in determining the truth or falsity of conclusions drawn from a hypothesis. And if it be asked how it is determined which of these functions a proposition is to have, the empirical answer is that this is determined in discourse. Discourse depends on what the parties to it believe. If you deny what I assert, I may try to prove it by means of other propositions you admit; if we both agree on some propositions, we may set out to see what follows from them; if we are doubtful about any proposition, we may test it by its consequences. In general, discourse is possible when and only when persons come together who (a) agree about something, (b) either disagree, or wish to inquire, about something else. This position itself implies a common logic of assertion, implication and, I should add, definition. Apart from that logic, actual beliefs and observations are all that can be appealed to, and without them the process could not go on. Each of us (not excluding those who take a false view of logic) directs his inquiries and establishes his conclusions, in greater or less disagreement with others, by means of this mechanism of individual statements and particular inferences. The person who holds that there are higher truths has still to draw lower conclusions from them in the ordinary way (as it is inferred, e.g., from the “moral government of the universe” that a man is not dead after he has died); he who holds that there is a total truth can only advance towards it step by step. We have all to rely on what we find to be the case; unless we could say that a certain thing is so, we could not begin to discuss or inquire. And all this implies, I maintain, that science depends entirely on observation, i.e., on finding something to be the case, and on the use of syllogism, either for proof or for testing; or, more generally, on observation in connection with, and in distinction from, anticipation. This means that there is no distinction between empirical and rational science. Since everything that can be asserted can be denied or doubted, since deduction and hypothesis are always possible, all sciences are observational and experimental.