Summa Theologiae > First Part of the Second Part > Question 78. That cause of sin which is malice > Article 1. Whether anyone sins through certain malice
I answer that, Man like any other being has naturally an appetite for the good; and so if his appetite incline away to evil, this is due to corruption or disorder in some one of the principles of man: for it is thus that sin occurs in the actions of natural things. Now the principles of human acts are the intellect, and the appetite, both rational (i.e. the will) and sensitive. Therefore even as sin occurs in human acts, sometimes through a defect of the intellect, as when anyone sins through ignorance, and sometimes through a defect in the sensitive appetite, as when anyone sins through passion, so too does it occur through a defect consisting in a disorder of the will. Now the will is out of order when it loves more the lesser good. Again, the consequence of loving a thing less is that one chooses to suffer some hurt in its regard, in order to obtain a good that one loves more: as when a man, even knowingly, suffers the loss of a limb, that he may save his life which he loves more. Accordingly when an inordinate will loves some temporal good, e.g. riches or pleasure, more than the order of reason or Divine law, or Divine charity, or some such thing, it follows that it is willing to suffer the loss of some spiritual good, so that it may obtain possession of some temporal good. Now evil is merely the privation of some good; and so a man wishes knowingly a spiritual evil, which is evil simply, whereby he is deprived of a spiritual good, in order to possess a temporal good: wherefore he is said to sin through certain malice or on purpose, because he chooses evil knowingly.