This world-ending does not take place, because, though it be possible to dwell in contradiction, it is impossible to make it concrete and actual: God, that is to say Reality, does not permit this. Thus it happens that under the name of natural justice, two sorts of products have existed in turn, or sometimes a mixture of those two different products, which have nothing to do with the programme announced. On the one hand, projects of new laws that seemed better than the old or good by comparison with these judged more or less bad, have been proposed as natural or rational justice, and precisely for this reason the old laws were called unnatural and irrational and the new _rational and natural._ Just as passionate and erotic temperaments, uninstructed by the experience of their past, swear with the utmost seriousness that their new love will be _constant, eternal and their last,_ so man, when he creates new laws, is often seized with the illusion that his laws will not change as did the old ones, forgetting that the old ones were once young and that they "satisfied divers" in their heyday, to express oneself in the words of the old carnavalesque song. Those natural laws are historical, those eternal laws are transitory, like all the others. All know how in certain times and places, religious tolerance, freedom of trade, private property, constitutional monarchy, have been proclaimed eternal; and in others, the extirpation of unbelievers, commercial protection, communism, the republic, and anarchy. [Sidenote: _Natural justice as philosophy of the practical._] Universal concepts, which were nothing but the Principles of the philosophy of the practical themselves, have on the other hand had a tendency to be classed as natural justice and to surpass the transitory and contingent. They are certainly eternal and unchangeable, but no longer laws, for they are formal and not material. Thus treatises of natural justice have sometimes become simply treatises (sometimes very valuable) of the Philosophy of the practical and especially of Ethic.--When (as to tell the truth has generally been the case) a practical description has accompanied a general treatment of Ethic, leading to a series of proposals for social, judicial or political reform, there has then occurred a _mingling_ of two different productions, which we have mentioned, philosophy and casuistic. But a natural justice has always remained unachieved, because unachievable and contradictory. [Sidenote: _Critique of natural justice._]