Now, without a serious study of man, his natural faculties and their successive development, we shall never be able to make these necessary distinctions, or to separate, in the actual constitution of things, that which is the effect of the divine will, from the innovations attempted by human art
But as long as we are ignorant of the natural man, it is in vain for us to attempt to determine either the law originally prescribed to him, or that which is best adapted to his constitution.
Throwing aside, therefore, all those scientific books, which teach us only to see men such as they have made themselves, and contemplating the first and most simple operations of the human soul, I think I can perceive in it two principles prior to reason, one of them deeply interesting us in our own welfare and preservation, and the other exciting a natural repugnance at seeing any other sensible being, and particularly any of our own species, suffer pain or death. It is from the agreement and combination which the understanding is in a position to establish between these two principles, without its being necessary to introduce that of sociability, that all the rules of natural right appear to me to be derived-rules which our reason is afterwards obliged to establish on other foundations, when by its successive developments it has been led to suppress nature itself.
His duties toward others are not dictated to him only by the later lessons of wisdom and, so long as he does not resist the internal impulse of compassion, he will never hurt any other man, nor even any sentient being; except on those lawful occasions on which his own preservation is concerned and he is obliged to give himself the preference. By this method also we put an end to the time-honoured disputes concerning the participation of animals in natural law: for it is clear that, being destitute of intelligence and liberty, they cannot recognise that law; as they partake, however, in some measure of our nature, in consequence of the sensibility with which they are endowed, they ought to partake of natural rights so that mankind is subjected to a kind of obligation even toward the brutes. It appears, in fact, that if I am bound to do no injury to my fellow-creatures, this is less because they are rational than because they are sentient beings: and this quality, being common both to men and beasts, ought to entitle the latter at least to the privilege of not being wantonly ill-treated by the former.
All we can know with any certainty respecting this law is that, if it is to be a law, not only the wills of those it obliges must be sensible of their submission to it; but also, to be natural, it must come directly from the voice of nature
The very study of the original man, of his real wants, and the fundamental principles of his duty, is besides the only proper method we can adopt to obviate all the difficulties which the origin of moral inequality presents, on the true foundations of the body politic, on the reciprocal rights of its members, and on many other similar topics equally important and obscure.
If we look at human society with a calm and disinterested eye, it seems, at first, to show us only the violence of the powerful and the oppression of the weak. The mind is shocked at the cruelty of the one, or is induced to lament the blindness of the other; and as nothing is less permanent in life than those external relations, which are more frequently produced by accident than wisdom, and which are called weakness or power, riches or poverty, all human institutions seem at first glance to be founded merely on banks of shifting sand. It is only by taking a closer look, and removing the dust and sand that surround the edifice, that we perceive the immovable basis on which it is raised, and learn to respect its foundations. The political and moral investigations, therefore, to which the important question before us leads, are in every respect useful; while the hypothetical history of governments affords a lesson equally instructive to mankind.