As a matter of fact, the coexistence of these two modes of thought lasts so long as the positive spirit has not reached its complete expansion, so long as a more or less considerable portion of natural phenomena is still explained by their essence, their cause, or their end. But this cannot be indefinitely prolonged. The more the positive spirit progresses, the more the theological and metaphysical conception of the world loses ground, and it becomes more evident that we must make our choice. The unity of the understanding the _perfect logical coherence_, are at this price. The conciliation being set aside, the alternative either to think solely or not at all, according to the positive mode, presents itself. The traditionalists, and especially Joseph de Maistre, saw this aspect of the problem very clearly. Comte gives them very great credit for it. De Maistre admits no salvation for our society except in the complete return to the theological mode of thought. He thus attacks at its very source, or to put it more plainly, in its many sources, the spirit of modern philosophy. He does not spare Locke any more than the philosophers of the XVIII. century who proceed from him, Bacon any more than Locke; the promoters of the Reformation any more than Bacon. He understood that the XVIII. century came as a mighty conclusion of which the XVI. and XVII. centuries were the premisses, and that the great destructive syllogism had originated in a work of decomposition which began as early as the XIV. century. He is therefore perfectly consistent with himself, when he endeavours to combat this diabolical work, and to bring Europe back to the mental and religious condition of the Middle-ages. The re-establishment of the spiritual supremacy of the Pope would put an end to mental and moral anarchy. The catholic doctrine would restore to men’s minds that unity which is their supreme need. This solution fulfils ideally the conditions of the problem, but, as a matter of fact, the solution is impracticable. The tide of history cannot flow back. In order to bring men’s minds once again under the sway of that spiritual power which they freely accepted in the Middle-ages, we should also have to reconstitute the totality of the conditions in which they lived at that time. How can we wipe from the pages of history the discovery of America, the invention of printing, and so many other great social facts? How can we pretend that Copernicus, Kepler, Galileo, Descartes, Newton, and all the heralds of positive Science never existed? And if, presuming what is impossible, we should succeed in restoring the mental and moral unity of Christian society in the Middle-ages, how could we prevent the natural laws which have once brought about its decomposition, from producing again the same result?