The final cause of the difference in character between the passions which regard self-preservation, and those which are directed to the multiplication of the species, will illustrate the foregoing remarks yet further; and it is, I imagine, worthy of observation even upon its own account. As the performance of our duties of every kind depends upon life, and the performing them with vigor and efficacy depends upon health, we are very strongly affected with whatever threatens the destruction of either: but as we were not made to acquiesce in life and health, the simple enjoyment of them is not attended with any real pleasure, lest, satisfied with that, we should give ourselves over to indolence and inaction. On the other hand, the generation of mankind is a great purpose, and it is requisite that men should be animated to the pursuit of it by some great incentive. It is therefore attended with a very high pleasure; but as it is by no means designed to be our constant business, it is not fit that the absence of this pleasure should be attended with any considerable pain. The difference between men and brutes, in this point, seems to be remarkable. Men are at all times pretty equally disposed to the pleasures of love, because they are to be guided by reason in the time and manner of indulging them. Had any great pain arisen from the want of this satisfaction, reason, I am afraid, would find great difficulties in the performance of its office. But brutes that obey laws, in the execution of which their own reason has but little share, have their stated seasons; at such times it is not improbable that the sensation from the want is very troublesome, because the end must be then answered, or be missed in many, perhaps forever; as the inclination returns only with its season. SECTION X. OF BEAUTY.