Had I to address nations still destitute of the light of religion, I would say that there is yet another considerable difference between adultery and other crimes. For it springs from the abuse of a constant and universal human impulse, an impulse anterior to, nay, the cause of the institution of society; whereas other crimes, destructive of society, derive their origin rather from momentary passions than from a natural impulse. To anyone cognisant of history and his kind, such an impulse will seem to be equivalent in the same climate to a constant quantity; and if this be so, those laws and customs which seek to diminish the sum-total will be useless or dangerous, because their effect will be to burthen one half of humanity with its own needs and those of others; but those laws, on the contrary, will be the wisest, which following, so to speak, the gentle inclination of the plain, divide the total amount, causing it to ramify into so many equal and small portions, that aridity or overflowing are equally prevented everywhere. Conjugal fidelity is always proportioned to the number and to the freedom of marriages. Where marriages are governed by hereditary prejudices, or bound or loosened by parental power, there the chains are broken by secret intrigue, in despite of ordinary morality, which, whilst conniving at the causes of the offence, makes it its duty to declaim against the results. But there is no need of such reflections for the man who, living in the light of true religion, has higher motives to correct the force of natural effects. Such a crime is of so instantaneous and secret commission, so concealed by the very veil the laws have drawn round it (a veil necessary, indeed, but fragile, and one that enhances, instead of diminishing, the value of the desired object), the occasions for it are so easy, and the consequences so doubtful, that the legislator has it more in his power to prevent than to punish it. As a general rule, in every crime which by its nature must most frequently go unpunished, the penalty attached to it becomes an incentive. It is a quality of our imagination, that difficulties, if they are not insurmountable nor too difficult, relatively to the mental energy of the particular person, excite the imagination more vividly, and place the object desired in larger perspective; for they serve as it were as so many barriers to prevent an erratic and flighty fancy from quitting hold of its object; and, while they compel the imagination to consider the latter in all its bearings, it attaches itself more closely to the pleasant side, to which our mind most naturally inclines, than to the painful side, which it places at a distance.