Of God and His Creatures2. A free agent is an agent that is cause of its own action (sui causa, sibi causa agendi). Agents that are determined (moventur) and act only inasmuch as they are determined by others, are not causes of their own acts. Only self-determining agents (moventia seipsa) have liberty of action; and these alone are guided in their action by judgement. A self-determining agent is made up of two elements, one determining and another determined. The element determined is the appetite; and that is determined either by intellect, or by phantasy, or by sense: for to these powers it belongs to judge. Of such self-determining agents, those alone judge freely which determine their own judgement. But no faculty of judging determines its own judgement unless it reflects upon its own act. If then it is to determine itself to judge, it must know its own judgement; and that knowledge belongs to intellect alone. Irrational animals then have a sort of free determination, or action, but not a free judgement (sunt quodammodo liberi quidem motus, sive actionis, non autem liberi judicii):* while inanimate things, being dependent for their every determination on things other than themselves, have not so much as free action, or determination. On the contrary, intelligent beings have not only free action, but also free judgement, which is having free will.*
3. An apprehension becomes a motive according as the thing apprehended takes the form of something good or suitable. In agents that determine their own movements,* the outward action goes upon some judgement pronouncing a thing good or suitable according as it is apprehended. If the agent pronouncing the judgement is to determine himself to judge,* he must be guided to that judgement by some higher form or idea in his apprehension.* This idea can be no other than the universal idea (ipsa ratio) of goodness or fitness, by aid whereof a judgement is formed of any given definite good, fit, or suitable thing. Therefore those agents alone determine themselves to judge, which have this general concept of goodness or fitness, -- that is to say, only intelligent agents. Therefore intelligent agents alone determine themselves, not only to act, but also to judge. They therefore alone are free in judging, which is having free will.
4. No movement or action follows from a general concept except by the medium of some particular apprehension, as all movement and action deals with particulars. Now the understanding naturally apprehends the universal. In order then that movement or any manner of action may follow upon the intellectual apprehension, the universal concept of the understanding must be applied to particular objects. But the universal contains in potentiality many particular objects. Therefore the application of the intellectual concept may be made to many divers objects; and consequently the judgement of the understanding about things to be done is not determined to one thing only.*
5. Some agents are without liberty of judgement, either because they have no judgement at all, as is the case with things that have no knowledge, as stones and plants, or because they have a judgement naturally determined to one effect, as irrational animals. For by natural reckoning* the sheep judges that the wolf is hurtful to it, and on this judgement flies from the wolf. But whatever agents have their judgement of things to be done not determined by nature to one effect, they must have free will. Such are all intelligent agents; for the understanding apprehends, not only this or that good, but good itself in general. Hence, since it is through the idea in apprehension that the understanding moves the will; and in all things the motive, or moving power, and the object moved must be proportioned to one another; it follows that the will of an intelligent subsistent being is not determined by nature except to good in general. Whatever therefore is presented to the will under the specific notion of good (sub ratione boni), the will may incline to it, without let or hindrance from any natural determination to the contrary. Therefore all intelligent agents have free will, arising out of the judgement of the understanding; and free will is defined 'a free judgement on the matter of a specific notion, or general concept.'*
2.47 : That Subsistent Intelligences are Voluntary Agents
2.49 : That Subsistent Intelligence is not Corporeal