It is important to insist that this question, limited as it is, is the utmost, to which, with any knowledge we have at present or are likely to have for a long time to come, Practical Ethics can hope to give an answer. I have already pointed out that we cannot hope to discover which is the best possible alternative in any given circumstances, but only which, among a few, is better than the others. And I have also pointed out that there is certainly no more than a probability, even if we are entitled to assert so much, that what is better in regard to its immediate effects will also be better on the whole. It now remains to insist that, even with regard to these immediate effects, we can only hope to discover which, among a few alternatives, will generally produce the greatest balance of good in the immediate future. We can secure no title to assert that obedience to such commands as “Thou shalt not lie,” or even “Thou shalt do no murder,” is universally better than the alternatives of lying and murder. Reasons why no more than a general knowledge is possible have been already given in Chap. I (§ 16); but they may be recapitulated here. In the first place, of the effects, which principally concern us in ethical discussions, as having intrinsic value, we know the causes so little, that we can scarcely claim, with regard to any single one, to have obtained even a hypothetical universal law, such as has been obtained in the exact sciences. We cannot even say: If this action is performed, under exactly these circumstances, and if no others interfere, this important effect, at least, will always be produced. But, in the second place, an ethical law is not merely hypothetical. If we are to know that it will always be better to act in a certain way, under certain circumstances, we must know not merely what effects such actions will produce, provided no other circumstances interfere, but also that no other circumstances will interfere. And this it is obviously impossible to know with more than probability. An ethical law has the nature not of a scientific law but of a scientific prediction: and the latter is always merely probable, although the probability may be very great. An engineer is entitled to assert that, if a bridge be built in a certain way, it will probably bear certain loads for a certain time; but he can never be absolutely certain that it has been built in the way required, nor that, even if it has, some accident will not intervene to falsify his prediction. With any ethical law, the same must be the case; it can be no more than a generalisation: and here, owing to the comparative absence of accurate hypothetical knowledge, on which the prediction should be based, the probability is comparatively small. But finally, for an ethical generalisation, we require to know not only what effects will be produced, but also what are the comparative values of those effects; and on this question too, it must be admitted, considering what a prevalent opinion Hedonism has been, that we are very liable to be mistaken. It is plain, then, that we are not soon likely to know more than that one kind of action will generally produce better effects than another; and that more than this has certainly never been proved. In no two cases will all the effects of any kind of action be precisely the same, because in each case some of the circumstances will differ; and although the effects, that are important for good or evil, may be generally the same, it is extremely unlikely that they will always be so.
95. (c) If, now, we confine ourselves to a search for actions which are generally better as means than any probable alternative, it seems possible to establish as much as this in defence of most of the rules most universally recognised by Common Sense. I do not propose to enter upon this defence in detail, but merely to point out what seem to be the chief distinct principles by the use of which it can be made.
In the first place, then, we can only show that one action is generally better than another as a means, provided that certain other circumstances are given. We do, as a matter of fact, only observe its good effects under certain circumstances; and it may be easily seen that a sufficient change in these would render doubtful what seem the most universally certain of general rules. Thus, the general disutility of murder can only be proved, provided the majority of the human race will certainly persist in existing. In order to prove that murder, if it were so universally adopted as to cause the speedy extermination of the race, would not be good as a means, we should have to disprove the main contention of pessimism—namely that the existence of human life is on the whole an evil. And the view of pessimism, however strongly we may be convinced of its truth or falsehood, is one which never has been either proved or refuted conclusively. That universal murder would not be a good
