something apart and sui generis; it is not even perceived at all. We perceive only their relation in time and space, and it is our mind which raises a succession to the height of a causal connection, by intercalating between cause and effect something of what we ourselves feel when we voluntarily order the execution of a movement. This is not the place to inquire what are the experimental conditions in which we subject phenomena to this anthropomorphic transformation; it will suffice for us to repeat here that, in perception, a chance relation between phenomena impresses us in the same way as when it is the expression of a law.
Our intellectual machine sometimes works in accord with the external law and at others makes mistakes and goes the wrong way. Then we are obliged to correct it, and to try a better adjustment, either by profounder experimenting with nature (methods of concordance, discordance, variations, &c.), or by a comparison of different judgments and arguments made into a synthesis; and this collaboration of several concordant activities ends in a conclusion which can never represent the truth, but only the probable truth. The study of the laws of the mind shows us too clearly, in fact, their fluidity with regard to the laws of nature for us not to accept probabilism. There exists no certitude—only very
