Thomas Aquinas

“ Not everyone that sells at a higher price than he bought is a tradesman, but only he who buys that he may sell at a profit. If, On the contrary, he buys not for sale but for possession, and afterwards, for some reason wishes to sell, it is not a trade transaction even if he sell at a profit. For he may lawfully do this, either because he has bettered the thing, or because the value of the thing has changed with the change of place or time, or on account of the danger he incurs in transferring the thing from one place to another, or again in having it carried by another. ”

“ The greedy tradesman blasphemes over his losses; he lies and perjures himself over the price of his wares. But these are vices of the man, not of the craft, which can be exercised without these vices. ”

“ Now the seller who offers goods for sale, gives the buyer an occasion of loss or danger, by the very fact that he offers him defective goods, if such defect may occasion loss or danger to the buyer---loss, if, by reason of this defect, the goods are of less value, and he takes nothing off the price on that account---danger, if this defect either hinder the use of the goods or render it hurtful, for instance, if a man sells a lame for a fleet horse, a tottering house for a safe one, rotten or poisonous food for wholesome. ”

“ For sometimes it happens that the seller thinks his goods to be specifically of lower value, as when a man sells gold instead of copper, and then if the buyer be aware of this, he buys it unjustly and is bound to restitution: and the same applies to a defect in quantity as to a defect in quality. ”

“ The other kind of exchange is either that of money for money, or of any commodity for money, not on account of the necessities of life, but for profit, and this kind of exchange, properly speaking, regards tradesmen, according to the Philosopher (Polit. i, 3) . The former kind of exchange is commendable because it supplies a natural need: but the latter is justly deserving of blame, because, considered in itself, it satisfies the greed for gain, which knows no limit and tends to infinity. ”

“ Therefore the seller is not bound to state the defects of the thing sold.
Objection 3: Further, man needs more to know the road of virtue than to know the faults of things offered for sale. Now one is not bound to offer advice to all or to tell them the truth about matters pertaining to virtue, though one should not tell anyone what is false. Much less therefore is a seller bound to tell the faults of what he offers for sale, as though he were counseling the buyer. ”

“ Now whatever is established for the common advantage, should not be more of a burden to one party than to another, and consequently all contracts between them should observe equality of thing and thing. Again, the quality of a thing that comes into human use is measured by the price given for it, for which purpose money was invented, as stated in Ethic. ”

“ As Augustine says "this jester, either by looking into himself or by his experience of others, thought that all men are inclined to wish to buy for a song and sell at a premium. But since in reality this is wicked, it is in every man's power to acquire that justice whereby he may resist and overcome this inclination." ”

“ Hence, according to the Divine law, it is reckoned unlawful if the equality of justice be not observed in buying and selling: and he who has received more than he ought must make compensation to him that has suffered loss, if the loss be considerable. I add this condition, because the just price of things is not fixed with mathematical precision, but depends on a kind of estimate, so that a slight addition or subtraction would not seem to destroy the equality of justice. ”

“ Hence if the gold or silver produced by alchemists has not the true specific nature of gold and silver, the sale thereof is fraudulent and unjust, especially as real gold and silver can produce certain results by their natural action, which the counterfeit gold and silver of alchemists cannot produce. Thus the true metal has the property of making people joyful, and is helpful medicinally against certain maladies. Moreover real gold can be employed more frequently, and lasts longer in its condition of purity than counterfeit gold. ”

“ Thus, for instance, a man may intend the moderate gain which he seeks to acquire by trading for the upkeep of his household, or for the assistance of the needy: or again, a man may take to trade for some public advantage, for instance, lest his country lack the necessaries of life, and seek gain, not as an end, but as payment for his labor. ”

“ A third defect is on the part of the quality, for instance, if a man sell an unhealthy animal as being a healthy one: and if anyone do this knowingly he is guilty of a fraudulent sale, and the sale, in consequence, is illicit. ”

“ Hence trading, considered in itself, has a certain debasement attaching thereto, in so far as, by its very nature, it does not imply a virtuous or necessary end. Nevertheless gain which is the end of trading, though not implying, by its nature, anything virtuous or necessary, does not, in itself, connote anything sinful or contrary to virtue: wherefore nothing prevents gain from being directed to some necessary or even virtuous end, and thus trading becomes lawful. ”

“ The saying of Chrysostom refers to the trading which seeks gain as a last end. This is especially the case where a man sells something at a higher price without its undergoing any change. For if he sells at a higher price something that has changed for the better, he would seem to receive the reward of his labor. ”

“ The measures of salable commodities must needs be different in different places, on account of the difference of supply: because where there is greater abundance, the measures are wont to be larger. However in each place those who govern the state must determine the just measures of things salable, with due consideration for the conditions of place and time. ”

“ On the other hand if a man find that he derives great advantage from something he has bought, he may, of his own accord, pay the seller something over and above: and this pertains to his honesty.
Reply to Objection 1: As stated above (FS, Q [96] , A [2] ) human law is given to the people among whom there are many lacking virtue, and it is not given to the virtuous alone. Hence human law was unable to forbid all that is contrary to virtue ”

“ There is also another reason, because trading engages the mind too much with worldly cares, and consequently withdraws it from spiritual cares; wherefore the Apostle says (2 Tim. 2:4) : "No man being a soldier to God entangleth himself with secular businesses." Nevertheless it is lawful for clerics to engage in the first mentioned kind of exchange, which is directed to supply the necessaries of life, either by buying or by selling. ”