St. Thomas de Aquino
The soul united to the body may suffer in two ways: by physical or mental passion and animal passion. For bodily passion suffers when the body is injured.
In fact, being the soul the shape of the body, both have only to be, so if some damage affects the body suffers indirectly also the soul, for the being which has in common with the body.
Body and soul
St. Thomas distinguishes the diseases of the body and the soul, in this last identifies two types of disorder against reason and the other against nature.
In any being the perversion occurs when temperance own is composed of one thing: in man the disease of his body is caused by the alteration of the necessary harmony of the humors. Similarly the appetite perversion, which sometimes upsets the reason, is to failure of human diseases. This is a failure that can occur for two reasons when the harmony of a being is indivisible, but has a certain amplitude of values, as seen in the harmony of the humors of the human body: in fact the human nature remains intact, it is that the heat is greater than necessary, whether it registers a drop in temperature; the harmony of human life is preserved depending on the quality of various diseases.
So, in a first mode, such compensation can occur in this balance without exceeding the limits of human life, and then it will be called directly incontinence or human vice, as well as a human disease in which the body remains saved, it is the nature of man. Instead the balance of human diseases can alter the point of exceeding the limits of human life, becoming similar to the affections of a beast: for example, a lion, a bear or a pig. To this attitude we can name as "bestiality".
I mean by bestial provisions, for example, that of the woman who, they say, disembowel pregnant women and the fetuses were devoured, or those referred to feel pleasure, as they say, in the wild coasts of Pontus, some of which eat raw meat, other meats humans, yet others will provide each other the children to make a big meal, or what is told as Phalaris. These behaviors are bestial; but some are caused by disease or madness for some, as the man who gave his mother as a sacrifice and consumed, or that slave who ate the liver of his companion.
St. Thomas, which sometimes calls all these disorders without distinction "bestiality", designates especially due to the unrest with behavioral belonging to the soul, or belonging to the knowledge and inner emotions, that is, the internal senses and passions that follow them. A disorder of the inner life and affect sensitive soul with Genesis, as it is caused by bad habits.
St. Thomas then refers to trends against nature that have a more clearly morbid and perverse character, but one might wonder if the same qualification can be attributed, at least by analogy, to all the provisions to vice residing in part of the sensitive soul with the resulting cognitive disorders are those trends that alienate man from their natural disposition. These are "pathological" vices, are "passions" in the proper sense, since they deprive from a form, putting the subject outside the order of nature.
Vices against nature are not only contrary to reason, which is the specific difference of man, but also in what constitutes its kind, animalism. With mental illness this does not mean only an illness, but more precisely, a disease of the human dimension of the soul.
In the Summa Theological, St. Thomas also speaks of a (insanity soul or healthcare denial). Bodily health is destroyed by the fact that the body loses complexion due to the human species, so the spiritual insanity is because the human soul loses its provisions of the human species. And this can happen both in regard to the reason, for example when one loses the use, both related to the appetitive power.
Human vice is an affectivity inclination against right reason, in bestial or pathological defects it is a double reason of disorder: a mode of appetite (against right reason), and this is equal to the human vice; the other, in the matter itself, which does not match that of course proportioned man's appetite, which is why it is called contra nature.
St. Thomas, on the kinds of vices: The wickedness can affect the vices that are opposed to all the virtues: the ignorance which is opposed to prudence, cowardice is opposed to fortitude, intemperance which is opposed to temperance, cruelty which is opposed to meekness; against individual faults occur with the provisions that are bestial because of the distortion of nature, and others, however, who are morbid because of both physical illness and animal caused by a bad habit.
The vice of cruelty, contrary to the virtue of forgiveness, St. Thomas explains the difference of this sadism with the irascibility and cruelty:
Meekness, which directly relates to the anger, all rigor contrasts with the vice of fury which implies an excess of anger. Instead cruelty implies an excess in the punishment. If these attitudes are caused by an evil customs, which are controllable by reason, are outside the responsibility of the physician. You can learn to control these anti-natural tendencies, or you can succumb to them. But you can also be completely dominated by these passions, and not only have them.
The human vices, are, however, provisions against reason and against the sensitivity which can then be consent consciously becoming vicious habit. These trends cannot be defeated unless it has obtained the right and a strong will, and even more is essential to request the intervention of God with heartfelt pleas. He alone will be able to move from the inside in a mysterious way His grace as to take out the malicious roots of vices source of all evil.