This method is a difficult one to apply. The notion of harmony is a much vaguer one than that of agreement. We cannot assign any precise general rules for distinguishing facts which are sufficiently connected to form a whole, the harmony of whose parts would be conclusive; nor can we determine beforehand the duration and extent of that which may be taken to form a whole. Facts separated by half a century of time and a hundred leagues of space may confirm each other in such a way as to establish a popular usage (for example, among the ancient Germans); but they would prove nothing if they were taken from a heterogeneous society subject to rapid evolution (take, for example, French society in 1750, and again in 1800, in Alsace and in Provence). Here we have to study the relation between the facts. This brings us to the beginnings of historical construction; here is the transition from analytical to synthetic operations. VII. But it remains to consider cases of discordance between facts established by documents and other facts established by other methods. It happens sometimes that a fact obtained as an historical conclusion is in contradiction with a body of known historical facts, or with the sum of our knowledge of humanity founded on direct observation, or with a scientific law established by the regular method of an established science. In the first two cases the fact is only in conflict with history, psychology, or sociology, all imperfectly established sciences; we then simply call the fact _improbable_. If it is in conflict with a true science it becomes a _miracle_. What are we to do with an improbable or miraculous fact? Are we to admit it after examination of the documents, or are we to pass on and shelve the question? _Improbability_ is not a scientific notion; it varies with the individual. Each person finds improbable what he is not accustomed to see: a peasant would think the telephone much more improbable than a ghost; a king of Siam refused to believe in the existence of ice. It is important to know who precisely it is to whom the fact appears to be improbable. Is it to the mass who have no scientific culture? For these, science is more improbable than miracle, physiology than spiritualism; their notions of improbability are worthless. Is it to the man who possesses scientific culture? If so, we have to deal with that which seems improbable to a scientific mind, and it would be more accurate to say that the fact is contrary to the results of science--that there is disagreement between the direct observations of men of science and the indirect testimony of the documents. How is this conflict to be decided? The question has no great practical interest; nearly all the documents which relate miraculous facts are already open to suspicion on other grounds, and would be discarded by a sound criticism. But the question of miracles has raised such passions that it may be well to indicate how it affects the historian.[176]