The difficulty is not avoided by having recourse to the popular theory of a natural faculty, a sense or instinct, informing us of right and wrong. For--besides that the existence of such a moral instinct is itself one of the matters in dispute--those believers in it who have any pretensions to philosophy, have been obliged to abandon the idea that it discerns what is right or wrong in the particular case in hand, as our other senses discern the sight or sound actually present. Our moral faculty, according to all those of its interpreters who are entitled to the name of thinkers, supplies us only with the general principles of moral judgments; it is a branch of our reason, not of our sensitive faculty; and must be looked to for the abstract doctrines of morality, not for perception of it in the concrete. The intuitive, no less than what may be termed the inductive, school of ethics, insists on the necessity of general laws. They both agree that the morality of an individual action is not a question of direct perception, but of the application of a law to an individual case. They recognise also, to a great extent, the same moral laws; but differ as to their evidence, and the source from which they derive their authority. According to the one opinion, the principles of morals are evident _à priori_, requiring nothing to command assent, except that the meaning of the terms be understood. According to the other doctrine, right and wrong, as well as truth and falsehood, are questions of observation and experience. But both hold equally that morality must be deduced from principles; and the intuitive school affirm as strongly as the inductive, that there is a science of morals. Yet they seldom attempt to make out a list of the _à priori_ principles which are to serve as the premises of the science; still more rarely do they make any effort to reduce those various principles to one first principle, or common ground of obligation. They either assume the ordinary precepts of morals as of _à priori_ authority, or they lay down as the common groundwork of those maxims, some generality much less obviously authoritative than the maxims themselves, and which has never succeeded in gaining popular acceptance. Yet to support their pretensions there ought either to be some one fundamental principle or law, at the root of all morality, or if there be several, there should be a determinate order of precedence among them; and the one principle, or the rule for deciding between the various principles when they conflict, ought to be self-evident.