Reply Obj. 1:  The will is distinguished from nature as one kind of cause from another; for some things happen naturally and some are done voluntarily.  There is, however, another manner of causing that is proper to the will, which is mistress of its act, besides the manner proper to nature, which is determinate to one thing.  But since the will is founded on some nature, it is necessary that the movement proper to nature be shared by the will, to some extent:  just as what belongs to a previous cause is shared by a subsequent cause.  Because in every thing, being itself, which is from nature, precedes volition, which is from the will.  And hence it is that the will wills something naturally.

Reply Obj. 2:  In the case of natural things, that which is natural, as a result of the form only, is always in them actually, as heat is in fire.  But that which is natural as a result of matter, is not always in them actually, but sometimes only in potentiality:  because form is act, whereas matter is potentiality.  Now movement is “the act of that which is in potentiality” (Aristotle, Phys. iii, 1).  Wherefore that which belongs to, or results from, movement, in regard to natural things, is not always in them.  Thus fire does not always move upwards, but only when it is outside its own place. [The Aristotelian theory was that fire’s proper place is the fiery heaven, i.e. the Empyrean.] And in like manner it is not necessary that the will (which is reduced from potentiality to act, when it wills something), should always be in the act of volition; but only when it is in a certain determinate disposition.  But God’s will, which is pure act, is always in the act of volition.

Reply Obj. 3:  To every nature there is one thing corresponding, proportionate, however, to that nature.  For to nature considered as a genus, there corresponds something one generically; and to nature as species there corresponds something one specifically; and to the individualized nature there corresponds some one individual.  Since, therefore, the will is an immaterial power like the intellect, some one general thing corresponds to it, naturally which is the good; just as to the intellect there corresponds some one general thing, which is the true, or being, or “what a thing is.”  And under good in general are included many particular goods, to none of which is the will determined. ________________________

SECOND ARTICLE [I-II, Q. 10, Art. 2]

Whether the Will Is Moved, of Necessity, by Its Object?

Objection 1:  It seems that the will is moved, of necessity, by its object.  For the object of the will is compared to the will as mover to movable, as stated in De Anima iii, 10.  But a mover, if it be sufficient, moves the movable of necessity.  Therefore the will can be moved of necessity by its object.

Obj. 2:  Further, just as the will is an immaterial power, so is the intellect:  and both powers are ordained to a universal object, as stated above (A. 1, ad 3).  But the intellect is moved, of necessity, by its object:  therefore the will also, by its object.