There can, I think, be little doubt that, in the stringency with which it is usually laid down, it rests not upon the law of nature, but upon positive law, although unassisted nature is sufficient to lead men many steps in its direction. Considering the subject simply in the light of unaided reason, two rules comprise the whole duty of man. He must abstain from whatever injures happiness or degrades character. Under the first head, he must include the more remote as well as the immediate consequences of his act. He must consider how his partner will be affected by the union, the light in which society will view the connection, the probable position of the children to be born, the effect of these births, and also the effect of his example upon the well-being of society at large. Some of the elements of this calculation vary in different stages of society. Thus, public opinion in one age will reprobate, and therefore punish, connections which, in another age, are fully sanctioned; and the probable position of the children, as well as the effect of the births upon society, will depend greatly upon particular and national circumstances. Under the second head is comprised the influence of this intercourse in clouding or developing the moral feelings, lowering or elevating the tone of character, exciting or allaying the aberrations of the imagination, incapacitating men for pure affections or extending their range, making the animal part of our nature more or less predominant. We know, by the intuition of our moral nature, that this predominance is always a degraded, though it is not always an unhappy, condition. We also know that it is a law of our being, that powerful and beautiful affections, which had before been latent, are evoked in some particular forms of union, while other forms of union are peculiarly fitted to deaden the affections and to pervert the character.