BOOK V.

certain. For a sign only indicates something which is, does not bring to pass that of which it is the sign. We require to show beforehand that all things, without exception, happen of necessity in order that a preconception may be a sign of this necessity. Otherwise, if there is no such universal necessity, neither can any preconception be a sign of a necessity which exists not. Manifestly, too, a proof established on firm grounds of reason must be drawn not from signs and loose general arguments, but from suitable and necessary causes. But how can it be that things foreseen should ever fail to come to pass? Why, this is to suppose us to believe that the events which providence foresees to be coming were not about to happen, instead of our supposing that, although they should come to pass, yet there was no necessity involved in their own nature compelling their occurrence. Take an illustration that will help to convey my meaning. There are many things which we see taking place before our eyes—the movements of charioteers, for instance, in guiding and turning their cars, and so on. Now, is any one of these movements compelled by any necessity?'