The Christian world has been quite long enough teaching an irrational and absurd doctrine about conscience. They not only blunder as to its origin, but as to its nature and functions. Nearly every Christian writer defines conscience as an "inward monitor" to tell us right from wrong; a divine faculty enabling us to "_judge_ between the good and the bad;" a "_guide_ to conduct," &c, &c. In the light of our present mental science this definition of conscience is utterly false. Conscience is not an _intelligent_ faculty at all--it is simply a feeling. By modern metaphysics conscience has been relegated from the domain of the intellect to its proper place among the emotions. Hence it _decides_ nothing, _judges_ nothing as between right and wrong, or anything else, for that is a function of intellect. Conscience, instead of being a "guide" or "judge," is but a blind impulse needing itself to be guided. It is simply a feeling for the right--a thirsting for the good--but the _intellect_ must decide what _is_ right; and the nature and character of its decisions will depend upon various circumstances, such as organization, education, &c.; and the decisions of different individuals as to right and wrong will differ as those circumstances differ. We hear a great deal about "enlightening the conscience;" but it cannot be done. You might as well talk of enlightening a sunflower, which instinctively turns its head to the light; or a vine, which instinctively creeps up the portico. The intellect, however, may be enlightened. Reason, which is the only and ultimate arbiter and guide to conduct, may be enlightened; and we may thus modify, guide and direct the blind impulses of conscience. The truth is, conscience in man, such as it is, is a development--is acquired rather than innate; has been developed by Nature instead of "implanted" by God. The moral sense, without doubt, gradually developed in man as he rose in the scale of intelligence. Where there is little or no intelligence, the moral sense would be inapplicable and incongruous, and is not needed, hence does not exist. When it is required, Nature, in perfect keeping with all her other adaptations, develops it. Darwin, in the "Descent of Man," vol. i, pp. 68-9, says:-- "The following proposition seems to me in a high degree probable--namely, that any animal whatever, endowed with well-marked social instincts, would inevitably acquire a moral sense or conscience, as soon as its intellectual powers had become as well developed, or nearly as well developed, as in man." On this point John Stuart Mill also has the following in his "Utilitarianism," p. 45:-- "If, as is my own belief, the moral feelings are not innate, but acquired, they are not for that reason less natural." The reader is also referred to "Psychological Inquiries," by Sir B. Brodie, for further evidence on this subject.