To furnish the most unremitted excitements of this kind, and to urge man to further the gracious designs of Providence by the full cultivation of the earth, it has been ordained that population should increase much faster than food.  This general law (as it has appeared in the former parts of this Essay) undoubtedly produces much partial evil, but a little reflection may, perhaps, satisfy us, that it produces a great overbalance of good.  Strong excitements seem necessary to create exertion, and to direct this exertion, and form the reasoning faculty, it seems absolutely necessary, that the Supreme Being should act always according to general laws.  The constancy of the laws of nature, or the certainty with which we may expect the same effects from the same causes, is the foundation of the faculty of reason.  If in the ordinary course of things, the finger of God were frequently visible, or to speak more correctly, if God were frequently to change his purpose (for the finger of God is, indeed, visible in every blade of grass that we see), a general and fatal torpor of the human faculties would probably ensue; even the bodily wants of mankind would cease to stimulate them to exertion, could they not reasonably expect that if their efforts were well directed they would be crowned with success.  The constancy of the laws of nature is the foundation of the industry and foresight of the husbandman, the indefatigable ingenuity of the artificer, the skilful researches of the physician and anatomist, and the watchful observation and patient investigation of the natural philosopher.  To this constancy we owe all the greatest and noblest efforts of intellect.  To this constancy we owe the immortal mind of a Newton.

As the reasons, therefore, for the constancy of the laws of nature seem, even to our understandings, obvious and striking; if we return to the principle of population and consider man as he really is, inert, sluggish, and averse from labour, unless compelled by necessity (and it is surely the height of folly to talk of man, according to our crude fancies of what he might be), we may pronounce with certainty that the world would not have been peopled, but for the superiority of the power of population to the means of subsistence.  Strong and constantly operative as this stimulus is on man to urge him to the cultivation of the earth, if we still see that cultivation proceeds very slowly, we may fairly conclude that a less stimulus would have been insufficient.  Even under the operation of this constant excitement, savages will inhabit countries of the greatest natural fertility for a long period before they betake themselves to pasturage or agriculture.  Had population and food increased in the same ratio, it is probable that man might never have emerged from the savage state.  But supposing the earth once well peopled, an Alexander, a Julius Caesar, a Tamberlane, or a bloody revolution might irrecoverably thin the human race, and defeat the