It is a common mistake in morals to say that a man is to blame for an act because he "knew it was wrong." He may have been told that it was wrong. But until he feels that it is wrong, and believes that it is wrong, it is not true to say that he knows it is wrong; for he may only know that some other person says it is wrong, which is a very different thing.
For instance, it might be said in this way that I am wicked for listening to Beethoven on the Sabbath, "because I know that it is wrong." But I do not know that is wrong. I do not believe that it is wrong. I only know that some people say it is wrong.
So I claim that conscience is what a man's nature and teaching make it: that it is a habit of memory, and no more mysterious than the habit of smoking, or dropping the aspirate, or eating peas with a knife.
Let us now look at some of the scientific evidence.
SCIENCE AND CONSCIENCE
I will quote first from Darwin, "Descent of Man," Chapter 4:
The following proposition seems to me in a high degree probable, namely, that any animal whatever, endowed with well-marked social instincts, the parental and filial affections being here included, would inevitably acquire a moral sense or conscience as soon as its intellectual powers had become as well, or nearly as well, developed as in man.... Secondly, as soon as the mental faculties had become highly developed, images of all past actions and motives would be incessantly passing through the brain of each individual; and that feeling of dissatisfaction, or even misery, which invariably results, as we shall hereafter see, from any unsatisfied instinct would arise as often as it was perceived that the enduring and always present social instinct, had yielded to some other instinct, at the time stronger, but neither enduring in its nature nor leaving behind it a very vivid impression.
Now let us see what Darwin means. The social instincts include human sympathy and the desire for the company of our fellows; love of approbation, which is the desire to be loved, or to be thought well of, by our fellows; and gratitude, which is the love we pay back for the love which is given us:
These social instincts are sometimes so strong, even in animals, as to overcome the powerful maternal instinct; so that migratory birds, as Darwin shows, and as we all know who have read our Gilbert White, will go with the flock and leave their new broods defenceless and unprovided for.
The social instincts, then, are very strong, and they lead us to conform to social rule or sentiment.