The philosophy of sensation continually appeals to experience. We also invoke experience; and it is experience that has given us certain facts mentioned in the preceding lecture, which constitute the primary notions of common sense. We admit the facts that serve as a foundation for the system of interest, and reject the system. The facts are true in their proper bearing,--the system is false in attributing to them an excessive, limitless bearing; and it is false again in denying other facts quite as incontestable. A sound philosophy holds for its primary law to collect all real facts and respect the real differences that also distinguish them. What it pursues before all, is not unity, but truth.[192] Now the ethics of interest mutilate truth,--they choose among facts those that agree with them, and reject all the others, which are precisely the very facts of morality. Exclusive and intolerant, they deny what they do not explain,--they form a whole well united, which, as an artificial work, may have its merit, but is broken to pieces as soon as it comes to encounter human nature with its grand parts. We are about to show that the ethics of interest, an offspring of the philosophy of sensation, are in contradiction with a certain number of phenomena, which human nature presents to whomsoever interrogates it without the spirit of system. 1st. We have established, not in the name of a system, but in the name of the most common experience, that entire humanity believes in the existence, in each of its members, of a certain force, a certain power that is called liberty. Because it believes in liberty in the individual, it desires that this liberty should be respected and protected in society. Liberty is a fact that the consciousness of each of us attests to him, which, moreover, is enveloped in all the moral phenomena that we have signalized, in moral approbation and disapprobation, in esteem and contempt, in admiration and indignation, in merit and demerit, in punishment and reward. We ask the philosophy of sensation and the ethics of interest what they do with this universal phenomena which all the beliefs of humanity suppose, on which entire life, private and public, turns. Every system of ethics, whatever it may be, which contains, I do not say a rule, but a simple advice, implicitly admits liberty. When the ethics of interest advise a man to sacrifice the agreeable to the useful, it apparently admits that man is free to follow or not to follow this advice. But in philosophy it does not suffice to admit a fact, there must be the right to admit it. Now, most moralists of interest deny the liberty of man, and no one has the right to admit it in a system that derives the entire human soul, all its faculties as well as all its ideas, from sensation alone and its developments.