Thomas Aquinas

“ Now in the avoidance of sorrow the order observed is that man at first flies from unpleasant objects, and secondly he even struggles against such things as cause sorrow. Now spiritual goods which are the object of the sorrow of sloth, are both end and means. Avoidance of the end is the result of "despair," while avoidance of those goods which are the means to the end, in matters of difficulty which come under the counsels, is the effect of "faint-heartedness," and in matters of common righteousness, is the effect of "sluggishness about the commandments." ”

“ Wherefore if the sin be a mere beginning of sin in the sensuality alone, without attaining to the consent of reason, it is a venial sin on account of the imperfection of the act. Thus in the genus of adultery, the concupiscence that goes no further than the sensuality is a venial sin, whereas if it reach to the consent of reason, it is a mortal sin. So too, the movement of sloth is sometimes in the sensuality alone, by reason of the opposition of the flesh to the spirit, and then it is a venial sin ”

“ Sloth is opposed to the precept about hallowing the Sabbath day. For this precept, in so far as it is a moral precept, implicitly commands the mind to rest in God: and sorrow of the mind about the Divine good is contrary thereto.
Reply to Objection 2: Sloth is not an aversion of the mind from any spiritual good, but from the Divine good, to which the mind is obliged to adhere. Wherefore if a man is sorry because someone forces him to do acts of virtue that he is not bound to do, this is not a sin of sloth; but when he is sorry to have to do something for God's sake. ”

“ And since the sensitive appetite has a bodily organ, it follows that on account of some bodily transmutation a man becomes apt to commit some particular sin. Hence it may happen that certain sins may become more insistent, through certain bodily transmutations occurring at certain fixed times. Now all bodily effects, of themselves, dispose one to sorrow; and thus it is that those who fast are harassed by sloth towards mid-day, when they begin to feel the want of food, and to be parched by the sun's heat. ”

“ The struggle against spiritual goods that cause sorrow is sometimes with men who lead others to spiritual goods, and this is called "spite"; and sometimes it extends to the spiritual goods themselves, when a man goes so far as to detest them, and this is properly called "malice." In so far as a man has recourse to eternal objects of pleasure, the daughter of sloth is called "wandering after unlawful things." ”

“ But it must be observed with regard to all sins that are mortal in respect of their genus, that they are not mortal, save when they attain to their perfection. Because the consummation of sin is in the consent of reason: for we are speaking now of human sins consisting in human acts, the principle of which is the reason. ”

“ Art. 2 - Whether sloth is a special vice? Objection 1: It would seem that sloth is not a special vice. For that which is common to all vices does not constitute a special kind of vice. But every vice makes a man sorrowful about the opposite spiritual good: for the lustful man is sorrowful about the good of continence, and the glutton about the good of abstinence. Since then sloth is sorrow for spiritual good, as stated above (A [1] ) , it seems that sloth is not a special sin. ”

“ This tendency to wander, if it reside in the mind itself that is desirous of rushing after various things without rhyme or reason, is called "uneasiness of the mind," but if it pertains to the imaginative power, it is called "curiosity"; if it affect the speech it is called "loquacity"; and in so far as it affects a body that changes place, it is called "restlessness of the body," when, to wit, a man shows the unsteadiness of his mind, by the inordinate movements of members of his body; while if it causes the body to move from one place to another, it is called "instability" ”