Thus, in everything, acting forms but a single genus along with
reacting, which (by the Aristotelians) is considered its opposite.
Reacting is what follows acting, without being its contrary; to be
burnt, for instance, follows burning, but is not its contrary. In
this case, the reaction is what results in the object itself from the
fact of burning, or of being burnt, which form but one (process),
whether the result be suffering, or something else, as, for instance,
depreciation. It might be objected, When one (being) makes another
suffer, is it not true that the one acts, and the other reacts?
Here from a single actualization result two facts, an action, and a
reaction. Besides, it is not necessary to include in the action the
will to cause suffering; it has only produced something else as a
result of which it causes suffering, something which occurring in the
being that suffers, and being one single (occurrence), that causes
suffering. What then is this one identical thing which is anterior to
the suffering? When there is no suffering, is there not nevertheless
a reaction in him in whom is the modification? For instance, in him
who hears? No: to hear is not to react, and sensation is not really
a reaction;[278] but to suffer is to experience a reaction, and the
reaction is not the contrary of the action (in the sense we have
explained).