Section — Slater, Manual of Moral Theology
Section IV. Violence
Violence or coercion is the using of greater force than can be resisted to compel another to perform some action against his will. In certain connections the person who suffers violence is said in English law to be under duress.
It follows from the definition that violence is from something external to the agent; no one can offer violence to himself; and that the subject resists to the utmost of his power.
If the resistance is only partial, there is violence only under a certain respect (secundum quid).
p. i, 17–18
The elicited acts of the will cannot be forced by violence, for in that case the agent would will and not will at the same time.
p. i, 18
The other internal faculties, and much more the external faculties of man, may be subject to violence. If the violence is absolute, the resulting action is involuntary and not imputable to him who suffers violence; if the resistance is only partial, the action will be voluntary to a certain extent, and in the same degree it will be imputable to the agent (Can. 2205, 52215, Sec, 2).
p. i, 18