§3. But though probably all moral agents have experience of such particular intuitions, and though they constitute a great part of the moral phenomena of most minds, comparatively few are so thoroughly satisfied with them, as not to feel a need of some further moral knowledge even from a strictly practical point of view. For these particular intuitions do not, to reflective persons, present themselves as quite indubitable and irrefragable: nor do they always find when they have put an ethical question to themselves with all sincerity, that they are conscious of clear immediate insight in respect of it. Again, when a man compares the utterances of his conscience at different times, he often finds it difficult to make them altogether consistent: the same conduct will wear a different moral aspect at one time from that which it wore at another, although our knowledge of its circumstances and conditions is not materially changed. Further, we become aware that the moral perceptions of different minds, to all appearance equally competent to judge, frequently conflict: one condemns what another approves. In this way serious doubts are aroused as to the validity of each man's particular moral judgments: and we are led to endeavour to set these doubts at rest by appealing to general rules, more firmly established on a basis of common consent.
And in fact, though the view of conscience above discussed is one which much popular language seems to suggest, it is not that which Christian and other moralists have usually given. They have rather represented the process of conscience as analogous to one of jural reasoning, such as is conducted in a Court of Law. Here we have always a system of universal rules given, and any particular action has to be brought under one of these rules before it can be pronounced lawful or unlawful. Now the rules of positive law are usually not discoverable by the individual's reason: this may teach him that law ought to be obeyed, but what law is must, in the main, be communicated to him from some external authority. And this is not unfrequently the case with the conscientious reasoning of ordinary persons when any dispute or difficulty forces them to reason: they have a genuine impulse to conform to the right rules of conduct, but they are not conscious, in difficult or doubtful cases, of seeing for themselves what these are: they have to inquire of their priest, or their sacred books, or perhaps the common opinion of the society to which they belong. In so far as this is the case we cannot strictly call their method Intuitional. They follow rules generally received, not intuitively apprehended. Other persons, however (or perhaps all to some extent), do seem to see for themselves the truth and bindingness of all or most of these current rules. They may still put forward `common consent' as an argument for the validity of these rules: but only as supporting the individual's intuition, not as a substitute for it or as superseding it.
Here then we have a second Intuitional Method: of which the fundamental assumption is that we can discern certain general rules with really clear and finally valid intuition. It is held that such general rules are implicit in the moral reasoning of ordinary men, who apprehend them adequately for most practical purposes, and are able to enunciate them roughly; but that to state them with proper precision requires a special habit of contemplating clearly and steadily abstract moral notions. It is held that the moralist's function then is to perform this process of abstract contemplation, to arrange the results as systematically as possible, and by proper definitions and explanations to remove vagueness and prevent conflict. It is such a system as this which seems to be generally intended when Intuitive or a priori morality is mentioned, and which will chiefly occupy us in Book iii.