23. Definition.--Those acts are called human of which a man is the master, and he is master of his actions in virtue of his reason and his will, which faculties make him superior to non-human agents that act without reason and freedom. Hence, the following kinds of acts done by a human being are not called human: (a) those that are not under the control of the mind, because one is permanently or temporarily without the use of reason or without knowledge (e.g., the acts done by the insane; by those who are unconscious or delirious, under the influence of hypnotism or drugs, distracted or carried away by vehement fear, anger, etc.; by infants and uninstructed persons); (b) those that are not under the control of the will, even though they are known (e.g., automatic acts, such as the acts of the vegetative powers, growth, circulation of the blood; pathological acts, such as convulsions; acts done under external violence). 24. Knowledge Requisite for a Human Act.--An act is human, or voluntary, when it is deliberately desired; and, since nothing can be deliberately desired unless it is known, an act done without knowledge is not human or voluntary. Thus, a delirious patient does not will the language he uses, for his mind is confused and he does not understand what he is saying. 25. The condition of a person without knowledge is ignorance, which is defined as the absence of knowledge in one who is capable of knowing. Ignorance is of various kinds. From the viewpoint of that which is not known (i.e., of the object of the ignorance), there is ignorance of the substance of an act and ignorance of the quality of an act. For example, Titus driving rapidly in the dark runs over and kills a pet animal of his neighbor, but knows nothing of this happening (ignorance of the substance of the act); Balbus, a child, fires a pistol at his playmate, not knowing that this causes death (ignorance of the physical quality of an act), and that it is the sin of murder (ignorance of the moral quality of an act). 26. With reference to the will of the person who is ignorant, three kinds of ignorance may be distinguished. (a) Ignorance is concomitant (simultaneous with the act of the will), when it is not voluntary, and yet is not therefore the reason of the act that follows it, since that act would have been done, even had there been knowledge. This may be illustrated by the example of a hunter who intended to kill an enemy, and killed him only accidentally while shooting at an animal.