2. Of no thing is the use evil in itself unless the thing itself be evil in itself.* But no food is in its nature evil; because everything is in its nature good (Chap. VII); albeit some particular food may be evil to some particular person, inasmuch as it makes against his bodily health. Therefore of no food, considered as such and such a thing, is the partaking a sin in itself: but it may be a sin, if a person uses it irrationally and not to his health.
3. To apply things to the purpose for which they exist is not in itself evil. But plants exist for the sake of animals, some animals for the sake of others, and all for the sake of man (Chap. LXXXI). Therefore to use either plants, or the flesh of animals, either for eating, or for any other purpose for which they are useful to man (vel ad quidquid aliud sunt homini utilia), is not in itself a sin.
4. The defect which makes sin redounds from soul to body, but not backwards from body to soul: for by sin we mean a disorder of the will. But articles of food concern the body immediately, not the soul. Therefore the taking of various foods cannot be in itself a sin, except in so far as it is inconsistent with rectitude of will. And that may come to be in several ways: in one way by some inconsistency with the proper end of food, as when for the pleasure of eating one uses food that disagrees with health either in kind or in quantity. Another way would be when the food becomes not the condition of him who eats it, or of the society in which he lives, as when one is more nice in his food than his means will allow, or violates the social conventions of those with whom he sits at table. A third way would be in the case of certain foods prohibited by some special law: thus in the Old Law sundry meats were forbidden for what they signified; and in Egypt of old the eating of beef was prohibited, lest agriculture should suffer;* and again there is the case of rules prohibiting the use of certain foods in order to check the lower appetites.*
Hence the Lord says: Not what entereth in at the mouth defiles a man (Matt. xv, 11).* Since eating and the intercourse of the sexes are not things in themselves unlawful, and exterior possessions are necessary for getting food, for rearing and supporting a family, and other bodily wants, it follows that neither is the possession of wealth in itself unlawful, provided the order of reason be observed, -- I mean, provided the man possesses justly the things that he has, and does not fix the final end of his will in them,* and uses them duly for his own and others' profit.
Hereby is excluded the error of some, who, as Augustine says, "most arrogantly called themselves Apostolics, because they did not receive into their communion married men and proprietors, such as are many monks and clerks whom the Catholic Church now contains: these people are heretics, because, separating themselves from the Church, they think that there is no hope for other persons who make use of what they do without" (De haeresibus, c. 40).*
3.126 : That not all Sexual Intercourse is Sin
3.128 : How the Law of God relates a man to his Neighbour