feel a resistance and an abhorrence of himself, so that he must put
a force on himself. It is impossible to explain the phenomenon that at
this parting of the ways (where the beautiful fable places Hercules
between virtue and sensuality) man shows more propensity to obey
inclination than the law. For, we can only explain what happens by
tracing it to a cause according to physical laws; but then we should
not be able to conceive the elective will as free. Now this mutually
opposed self-constraint and the inevitability of it makes us recognize
the incomprehensible property of freedom.



The impulses of nature, then, contain hindrances to the fulfilment
of duty in the mind of man, and resisting forces, some of them
powerful; and he must judge himself able to combat these and to
conquer them by means of reason, not in the future, but in the
present, simultaneously with the thought; he must judge that he can do
what the law unconditionally commands that be ought.

Now the power and resolved purpose to resist a strong but unjust
opponent is called fortitude (fortitudo), and when concerned with
the opponent of the moral character within us, it is virtue (virtus,
fortitudo moralis). Accordingly, general deontology, in that part
which brings not external, but internal, freedom under laws is the
doctrine of virtue.

{INTRODUCTION ^paragraph 10}

Jurisprudence had to do only with the formal condition of external
freedom (the condition of consistency with itself, if its maxim became