Instinct is something which transcends knowledge. We have, undoubtedly, certain finer fibers that enable us to perceive truths when logical deduction, or any other willful effort of the brain, is futile.
Surely we have always acted; it is an instinct inherent in all of us. Some of us are better at it than others, but we all do it.
So the lion is the law-breaker. Just as to the primitive man the lion is the lawbreaker, the great nuisance, dangerous to human beings and to animals, that breaks into the Kraal at night and fetches the bull out of the herd: he is the destructive instinct.
I believe there exists, and I feel within me, an instinct for truth, or knowledge or discovery, of something of the same nature as the instinct of virtue, and that our having such an instinct is reason enough for scientific researches without any practical results ever ensuing from them.
A man who has no assured and ever present belief in the existence of a personal God or of a future existence with retribution and reward, can have for his rule of life, as far as I can see, only to follow those impulses and instincts which are the strongest or which seem to him the best ones.