12. Intelligence is revealed by voluntary, reflective, premeditated, united actions, according to the fitness of circumstances. It is incontestably an exclusive attribute of the soul.
All mechanical action is instinctive; that which denotes reflection and contrivance is intelligent. One is free; the other is not.
Instinct is a sure guide which never deceives; intelligence, solely because it is unrestrained, is sometimes subject to error.
If the instinctive action has not the character of the intelligent one, it reveals, nevertheless, an intelligent cause, essentially provident. If one admits that instinct has its source in matter, it is necessary, also, to admit that matter is intelligent, - surely wiser and more foreseeing than the soul, since instinct does not deceive, whilst intelligence does.
If one considers instinct to be rudimental intelligence, why is it, in certain cases, superior to reasoning intelligence - that it makes possible the execution of things that the latter cannot produce?
If it is the attribute of a special spiritual principle, what becomes of this principle? When instinct is effaced, this principle must also be destroyed. If animals are only endowed with instinct, their future is without issue; their sufferings have no compensation. This would be in conformity with neither the justice, nor the goodness of God. (Chap. II, n°19).