Man is man because he chanced to develop intelligence instead of instinct; otherwise he would to this day have remained among the anthropoid apes. He has turned away from nature, become unnatural, as it were, disliked the earth upon which he found himself, and changed the face of it somewhat to his liking.
Jack LondonThe pitch to which he was aroused was tremendous. All the fighting blood of his breed was up in him and surging through him. This was living., though he did not know it. He was realizing his own meaning in the world; he was doing that for which he was made.... He was justifying his existence, than which life can do no greater; for life achieves its summit when it does to the uttermost that which it was equipped to do.
Jack London