Philosophy, Bradley has said, is an attempt to gain a view of the general nature of Reality which will satisfy the intellect. This definition, which looks innocent enough, nevertheless suggests strongly the necessity of a certain preliminary inquiry as an indispensable basis of all philosophical construction. We ought to ask at the beginning, 'What in general would satisfy the intellect?' or 'What are the formal characteristics of that which the intellect is prepared to accept as real?' Just how fruitful such an investigation may prove for subsequent construction will depend, naturally, upon the sort of answer which our question induces. But it is hard to see how any philosophy which pretends to be critical and ultimate - and surely these adjectives are implied in the very meaning of the word philosophy - can legitimately dispense with this preliminary. Our 'scientific' philosophies, of course, do commonly dispense with it. But it may well be asked whether it is not just the nemesis of such a method - or rather lack of method - that their several constructions are in agreement with one another upon scarcely one positive philosophic proposition of importance. Recent philosophy, for all its richness, has exhibited a truly chaotic instability. And the fundamental reason, in my judgment, is the failure to keep firmly before the mind that what is good enough for science is emphatically not good enough for philosophy. It is not science's task to ask of its principles that they should be rational through and through, capable of satisfying in full the demands which the intellect makes upon whatever lays claim to be finally 'real' But in respect of philosophic principles we can aim at nothing less. We may have to be content with something less. But if so, it will be of the first importance to know that, and if possible to see why, they are less.

It is assumed, of course, that the investigation in question is one upon which we can engage with some hope of achieving results. But this is an assumption which seems hardly doubtful. Thinking is a process directed towards the establishment of truth, of a 'content' which will adequately express the real. And it is a process which is, quite evidently, not haphazard, but marked by a well-defined continuity.1 To suppose it blind and 'aimless' would be, in effect, to render all argumentation futile, and would imply a refinement of scepticism which it is no purpose of these pages to advocate. It ought therefore to be possible, one may suppose, by careful scrutiny of the process of thinking, to lay bare the criterion which directs its activity and controls its advances from less to greater satisfaction.

1 It is not so evident, of course, to those who insist upon concentrating attention upon low-grade specimens of thinking, e.g. perception. And it may be remarked in passing that the modern preoccupation with the so-called 'problem of perception' seems out of all proportion to its real importance for philosophy. The manner in which this problem is broached - involving various assumptions of physical and physiological ' truths' - is such that its discussion is necessarily incompetent to make any contribution to the ultimate problem of knowledge. For the veridical character of physical and physiological knowledge is just taken for granted as the very basis of the discussion.

Now there is one mark, albeit a negative one, of the 'intellectually satisfying' concerning which there is no serious difference of opinion. From it we may make our start. The intellect will accept as genuinely expressing reality no content which contradicts itself. Controversy there may be as to what precisely constitutes a 'self-contradiction.' But no one with whom philosophy is called upon seriously to deal will refuse to allow that where there is that which he understands by 'contradiction,' there is defect of truth. Let us begin then by inquiring into the essential mark of the contradictory. Our discussion, as we shall find, will lead on naturally to the apprehension of an indispensable condition of the non-contradictory, and will accordingly yield us not merely negative but also some positive (though purely formal) information as to the general character of that which the intellect can accept as true and real.

What then is Contradiction? Its specific character will best disclose itself by reference to the logical nature of the unit of thought, 'judgment' or 'predication.'1

All judgment, all thinking, involves the assertion, in some sense, of 'unity' in 'diversity.' So much is obvious. We cannot possibly dispense either with the differences or with the unity. Unless the differences are pronounced to be in some sense 'one' we have not got a judgment but, at best, a mere 'association of ideas.' And unless it is 'differences' that we pronounce to be one, there is again no judgment, for there is no movement of thought at all. It is an old story that the formula of thinking cannot be 'A is A.' The predicate may, indeed, be verbally identical with the subject, but unless it is conceptually distinct we have got, not thinking, but a mere form of words.

Thinking then must unite differences. But if the formula of judgment is certainly not 'A is A,' is it more correctly expressed as 'A is B'? If we take this formula strictly as it stands, it seems evident that we are in no better case than before. For B, being different from A, is not-A. What the formula appears to say, therefore, is that 'A is not-A.' But this is to assert and to annul in the same act, which no one supposes to be other than crassly self-contradictory. If, then, the uniting of differents characteristic of thought is to find expression, it cannot be in the simple formula 'A is B.' For this, strictly interpreted, expresses rather what thought characteristically abhors than what thought characteristically affirms.

1 In what immediately follows I shall be doing little more than restating the grist of 'Note A.' already referred to.