In effect, alongside of religious authority, based on divine revelation and belonging to the clergy, there is now a lay authority founded on human reason, which is exercised by scientists, erudites, scholars and philosophers. They too, in their way, form a clergy, since they frame creeds and teach a faith; only, their preparatory and dominant disposition is not trust and a docile mind, but distrust and the need of critical examination. With them, nearly every source of belief is suspicious. At bottom, among the ways of acquiring knowledge, they accept but two, the most direct, the simplest, the best tested, and again on condition that one proves the other, the type of the first being that process of reasoning by which we show that two and two make four, and the second that experience by which we demonstrate that heat above a certain degree melts ice, and that cold below a certain degree freezes water. This is the sole process that is convincing; all others, less and less sure in proportion as they diverge from it, possess only a secondary, provisional and contestable value, that which it confers on them after verification and check.--Let us accordingly avail ourselves of this one, and not of another, to express, restrain or suspend our judgment. So long as the intellect uses it and only it, or its analogues, to affirm, set aside or doubt, it is called reason, and the truths thus obtained are definitive acquisitions. Acquired one by one, the truths thus obtained have for a long time remained scattered, in the shape of fragments; only isolated sciences have existed or bits of science. About the middle of the eighteenth century these separate parts became united and have formed one body, a coherent system. Out of this, formerly called philosophy, that is to say a view of nature as a whole, consisting of perfect order on lasting foundations, a sort of universal network which, suddenly enlarged, stretches beyond the physical world to the moral world, taking in man and men, their faculties and their passions, their individual and their collective works, various human societies, their history, customs and institutions, their codes and governments, their religions, languages, literatures and fine arts, their agriculture, industries, property, the family and the rest.[6233] Then also, in each natural whole the simultaneous or successive parts are connected together; a knowledge of their mutual ties is important, and, in the spiritual order of things, one accomplishes this, as in the material order, through scientific distrust, through critical examination, by credible experimentation and process.[6234]