The origin of the belief in free-will once understood, the reasons for its perpetuation are not difficult to discover. First comes the obscurity of the processes underlying human action. This alone would secure a certain vitality for a belief that has always made the impossibility of explaining the origin, sequence, and relation of mental states its principal defence. Beyond offering as evidence the questionable affirmation of consciousness volitionists have been unanimous in resting their case upon their adversary's want of knowledge. And it is further characteristic that while holding to a theory on behalf of which not a single shred of positive evidence has ever been produced, they yet demand the most rigorous and the most complete demonstration of determinism before they will accept it as true; this despite the presumptive evidence in its favour arising from the fact of its harmony with our knowledge in other directions. Secondly, the human mind does not at any time commence its philosophic speculations _de novo_. It necessarily builds upon the materials accumulated by previous generations; and usually retains the form in which previous thinking has been cast, even when the contents undergo marked modifications. Thus the ghost-soul of the savage, a veritable material copy of the body, by centuries of philosophizing gets refined into the distinct "spiritual" substance of the metaphysician. And this, not because the notion of a "soul" was derived from current knowledge or thinking, but because it was one of the inherited forms of thought to which philosophy had to accommodate itself. The result of this pressure of the past upon contemporary thinking is that a large proportion of mental activity is in each generation devoted to reconciling past theories of things with current knowledge. In our own time the number of volumes written to reconcile the theory of evolution with already existing religious views is a striking example of this phenomenon. And beyond the philosophic few there lies the mass of the people with whom an established opinion of any kind takes on something of a sacred character. Unfortunately, too, many writers work with an eye to the prejudices of this class, which prejudices are in turn strengthened by the tacit support of men of ability, or at least by their not openly controverting them. It is, however, of the greatest significance that since the opening of the modern scientific period, wherever qualified thinkers have deliberately based their conclusions upon contemporary knowledge the theory of determinism has been generally upheld.