ABSTRACT
Critical analysis yields in the result a number of conceptions and statements, accompanied by comments on the probability of the facts stated being accurate. Conceptions and statements are two different kinds of results, and must be treated by different methods. The possibility of proving an historical fact depends on the number of independent documents relating to it which have been preserved, and the preservation of the documents is a matter of chance; this explains the share which chance has in the formation of historical science. The facts which it is possible to establish are chiefly those which cover a large extent of space or time, customs, doctrines, institutions, great events; they were easier to observe than the others, 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.
