Thus again it has been called natural that men should form themselves into immense tribes or nations, and go to war with each other. Thus persons of narrow views and observation regard everything as natural and right that happens, however capriciously or for however short a time, to prevail in the society in which they live. The only things which can be said to compose the nature or constitution of man are our external structure, which itself is capable of being modified with indefinite variety; the appetites and impressions growing out of that structure; and the capacity of combining ideas and inferring conclusions. The appetites common to the species we cannot wholly destroy: the faculty of reason it would be absurd systematically to counteract, since it is only by some sort of reasoning, bad or good, that we can so much as adopt any system. In this sense therefore no doubt we ought to follow nature, that is, to employ our understandings and increase our discernment. But, by conforming ourselves to the principles of our constitution in this respect, we most effectually exclude all following, or implicit assent. If we would fully comport ourselves in a manner correspondent to our properties and powers, we must bring everything to the standard of reason. Nothing must be admitted either as principle or precept that will not support this trial. Nothing must be sustained because it is ancient, because we have been accustomed to regard it as sacred, or because it has been unusual to bring its validity into question. Finally, if by following nature be understood that we must fix our preference upon things that will conduce to human happiness, in this there is some truth. But the truth it contains is extremely darkened by the phraseology in which it is couched.
We must consider our external structure so far as relates to the mere question of our preservation. As to the rest, whatever will make a reasonable nature happy will make us happy; and our preference ought to be bestowed upon that species of pleasure which has most independence and most animation.