§2. There seem to be four conditions, the complete fulfilment of which would establish a significant proposition, apparently self-evident, in the highest degree of certainty attainable: and which must be approximately realised by the premises of our reasoning in any inquiry, if that reasoning is to lead us cogently to trustworthy conclusions.
I. The terms of the proposition must be clear and precise. The rival originators of modern Methodology, Descartes and Bacon, vie with each other in the stress that they lay on this point; and the latter's warning against the ``notiones male terminatæ'' of ordinary thought is peculiarly needed in ethical discussion. In fact my chief business in the preceding survey has been to free the common terms of Ethics, as far as possible, from objection on this score.
II. The self-evidence of the proposition must be ascertained by careful reflection. It is needful to insist on this, because most persons are liable to confound intuitions, on the one hand with mere impressions or impulses, which to careful observation do not present themselves as claiming to be dictates of Reason; and on the other hand, with mere opinions, to which the familiarity that comes from frequent hearing and repetition often gives a false appearance of self-evidence which attentive reflection disperses. In such cases the Cartesian method of testing the ultimate premises of our reasonings, by asking ourselves if we clearly and distinctly apprehend them to be true, may be of real use; though it does not, as Descartes supposed, afford a complete protection against error. A rigorous demand for self-evidence in our premises is a valuable protection against the misleading influence of our own irrational impulses on our judgments: while at the same time it not only distinguishes as inadequate the mere external support of authority and tradition, but also excludes the more subtle and latent effect of these in fashioning our minds to a facile and unquestioning admission of common but unwarranted assumptions.
And we may observe that the application of this test is especially needed in Ethics. For, on the one hand, it cannot be denied that any strong sentiment, however purely subjective, is apt to transform itself into the semblance of an intuition; and it requires careful contemplation to detect the illusion. Whatever we desire we are apt to pronounce desirable: and we are strongly tempted to approve of whatever conduct gives us keen pleasure. And on the other hand, among the rules of conduct to which we customarily conform, there are many which reflection shows to be really derived from some external authority: so that even if their obligation be unquestionable, they cannot be intuitively ascertained. This is of course the case with the Positive Law of the community to which we belong. There is no doubt that we ought,---at least generally speaking,---to obey this: but what it is we cannot of course ascertain by any process of abstract reflection, but only by consulting Reports and Statutes. Here, however, the sources of knowledge are so definite and conspicuous, that we are in no danger of confounding the knowledge gained from studying them with the results of abstract contemplation. The case is somewhat different with the traditional and customary rules of behaviour which exist in every society, supplementing the regulative operation of Law proper: here it is much more difficult to distinguish the rules which a moral man is called upon to define for himself, by the application of intuitively known principles, from those as to which some authority external to the individual is recognised as the final arbiter.
We may illustrate this by referring to two systems of rules which we have before compared with Morality; the Law of Honour, and the Law of Fashion or Etiquette. I noticed that there is an ambiguity in the common terms `honourable' and `dishonourable'; which are no doubt sometimes used, like ethical terms, as implying an absolute standard. Still, when we speak of the Code of Honour we seem to mean rules of which the exact nature is to be finally determined by an appeal to the general opinion of well-bred persons: we admit that a man is in a sense `dishonoured' when this opinion condemns him, even though we may think his conduct unobjectionable or even intrinsically admirable.  Similarly, when we consider from the point of view of reason the rules of Fashion or Etiquette, some may seem useful and commendable, some indifferent and arbitrary, some perhaps absurd and burdensome: but nevertheless we recognise that the final authority on matters of Etiquette is the custom of polite society; which feels itself under no obligation of reducing its rules to rational principles. Yet it must be observed that each individual in any society commonly finds in himself a knowledge not obviously incomplete of the rules of Honour and Etiquette, and an impulse to conform to them without requiring any further reason for doing so. Each often seems to see at a glance what is honourable and polite just as clearly as he sees what is right: and it requires some consideration to discover that in the former cases custom and opinion are generally the final authority from which there is no appeal. And even in the case of rules regarded as distinctly moral, we can generally find an element that seems to us as clearly conventional as the codes just mentioned, when we contemplate the morality of other men, even in our own age and country. Hence we may reasonably suspect a similar element in our own moral code: and must admit the great importance of testing rigorously any rule which we find that we have a habitual impulse to obey; to see whether it really expresses or can be referred to a clear intuition of rightness.
III. The propositions accepted as self-evident must be mutually consistent. Here, again, it is obvious that any collision between two intuitions is a proof that there is error in one or the other, or in both. Still, we frequently find ethical writers treating this point very lightly. They appear to regard a conflict of ultimate rules as a difficulty that may be ignored or put aside for future solution, without any slur being thrown on the scientific character of the conflicting formulæ. Whereas such a collision is absolute proof that at least one of the formulæ needs qualification: and suggests a doubt whether the correctly qualified proposition will present itself with the same self-evidence as the simpler but inadequate one; and whether we have not mistaken for an ultimate and independent axiom one that is really derivative and subordinate.
IV. Since it is implied in the very notion of Truth that it is essentially the same for all minds, the denial by another of a proposition that I have affirmed has a tendency to impair my confidence in its validity. And in fact `universal' or `general' consent has often been held to constitute by itself a sufficient evidence of the truth of the most important beliefs; and is practically the only evidence upon which the greater part of mankind can rely. A proposition accepted as true upon this ground alone has, of course, neither self-evidence nor demonstrative evidence for the mind that so accepts it; still, the secure acceptance that we commonly give to the generalisations of the empirical sciences rests---even in the case of experts---largely on the belief that other experts have seen for themselves the evidence for these generalisations, and do not materially disagree as to its adequacy. And it will be easily seen that the absence of such disagreement must remain an indispensable negative condition of the certainty of our beliefs. For if I find any of my judgments, intuitive or inferential, in direct conflict with a judgment of some other mind, there must be error somewhere: and if I have no more reason to suspect error in the other mind than in my own, reflective comparison between the two judgments necessarily reduces me temporarily to a state of neutrality. And though the total result in my mind is not exactly suspense of judgment, but an alternation and conflict between positive affirmation by one act of thought and the neutrality that is the result of another, it is obviously something very different from scientific certitude.
Now if the account given of the Morality of Common Sense in the preceding chapters be in the main correct, it seems clear that, generally speaking, its maxims do not fulfil the conditions just laid down. So long as they are left in the state of somewhat vague generalities, as we meet them in ordinary discourse, we are disposed to yield them unquestioning assent, and it may be fairly claimed that the assent is approximately universal---in the sense that any expression of dissent is eccentric and paradoxical. But as soon as we attempt to give them the definiteness which science requires, we find that we cannot do this without abandoning the universality of acceptance. We find, in some cases, that alternatives present themselves, between which it is necessary that we should decide; but between which we cannot pretend that Common Sense does decide, and which often seem equally or nearly equally plausible. In other cases the moral notion seems to resist all efforts to obtain from it a definite rule: in others it is found to comprehend elements which we have no means of reducing to a common standard, except by the application of the Utilitarian---or some similar---method. Even where we seem able to educe from Common Sense a more or less clear reply to the questions raised in the process of definition, the principle that results is qualified in so complicated a way that its self-evidence becomes dubious or vanishes altogether. And thus in each case what at first seemed like an intuition turns out to be either the mere expression of a vague impulse, needing regulation and limitation which it cannot itself supply, but which must be drawn from some other source: or a current opinion, the reasonableness of which has still to be shown by a reference to some other principle.
In order that this result may be adequately exhibited, I must ask the reader to travel with me again through the series of principles elicited from Common Sense in the previous chapters, and to examine them from a somewhat different point of view. Before, our primary aim was to ascertain impartially what the deliverances of Common Sense actually are: we have now to ask how far these enunciations can claim to be classed as Intuitive Truths.
The reader should observe that throughout this examination a double appeal is made; on the one hand to his individual moral consciousness, and, on the other hand, to the Common Sense of mankind, as expressed generally by the body of persons on whose moral judgment he is prepared to rely. I ask him (1) whether he can state a clear, precise, self-evident first principle, according to which he is prepared to judge conduct under each head: and (2) if so, whether this principle is really that commonly applied in practice, by those whom he takes to represent Common Sense.