Present, one may illogically deduce the inferribleness from the fixity and assign it as a cause of the fixity. And again, it is natural to assume a symmetry and reversibleness of relation between Past and Future which does not really exist, and thence to conclude that if one be fixed, the other must be so too. This argument is not that "from Causation," yet one seems to suggest the other. Now, however it be to the philosopher, Past and Future are not alike to the scientist. Even if physical causation be considered as reversible, many of the cycles of actual change are not. These cycles move in fixed directions, and not backward, even when they bring events and successive individuals or systems around to nearly the old conditions. And besides, there are changes going on which, as far as science can yet see, never will be unmade or offset by any cycle: for instance, the progressive residual concentration of mass and diffusion of heat, and the unceasing Loss of "motivity." Thus neither from moment to moment nor yet in the long run is the relation of Past to Future a reversible one.
But if the objection merely means this, "Since every effect or phenomenon has a cause, and this cause has a cause, etc., thus giving an infinite number of steps of causation between the effect and its first cause, therefore free volition cannot be a cause, for this infinite number of steps between it and its observed effect must take an infinite time," — if this be the supposed difficulty, then I think it turns upon the same fallacy as does the story of Achilles and the tortoise. We are told that he could not catch the tortoise, because while he ran 100 rods it crawled one; and while he ran that one it crawled 1100; and then 110000 and so on. Thus analyzed, the process did indeed require an infinite number of steps, but then these steps grew so rapidly shorter and shorter that the sum of all their lengths was finite, and might have been microscopic. Very likely it is as true in our problem as in that of Achilles, that one may rightly either introduce the infinite series or not: i.e. we may say "Everything is caused," and so bring in the infinite series, or say "Volition is its own cause" and stop there, replacing the series of steps by its resultant or quasi-sum.
