Answ. There may be some instances in trading with enemies, or with rich men, that regard not such matters, or with men that are supposed to know it as well as you, in which you are not bound to tell them. But in your ordinary equal trading, when you have reason to think that the buyer knoweth it not, and would not give so dear if he knew it, you are bound to tell him; because you must love your neighbour as yourself, and do as you would be done by, and not take advantage of his ignorance.
Quest. VIII. If I foresee a dearth, may I not keep my commodity till then?
Answ. Yes, unless it be to the hurt of the commonwealth; as if your keeping it in be the cause of the dearth, and your bringing it forth would help to prevent it.
Quest. IX. May one use many words in buying and selling?
Answ. You must use no more than are true, and just, and useful: but there are more words needful with some persons who are talkative and unsatisfied than with others.
Quest. X. May I buy as cheap as I can get it, or give less than the thing is worth?
Answ. If it be worth more to you than the market price, (through your necessity,) you are not bound to give above the market price. If it be worth less to you than the market price, you are not bound to give more than it is worth to you, as suited to your use. But you must not desire nor seek to get another's goods or labour for less than it is worth in both these respects (in common estimate, and to you).
Quest. XI. May I take advantage of another's necessity to buy for less than the worth, or sell for more: as e. g. a poor man must needs have money suddenly for his goods, though he sell them but for half the worth; and I have no need of them: am I bound to give him the worth when I have no need? and when it is a great kindness to him to give him any thing in that strait? So also when I have no desire to sell my horse, and another's necessity maketh him willing to give more than he is worth, may I not take it?
Answ. To the first case: you must distinguish between an act of justice and of charity; and between your need of the thing and the worth of it to you. Though you have no need of the poor man's goods, yet if you buy them, both justice and charity require that you give him as much as they are worth to you, though not so much as they are worth in the market: yea, and that you buy them of him in his necessity; for if you give him but what they are worth to you, you are no loser by it; and you should do another good, when it is not to your own hurt or loss. By what they are worth to you, I mean so much as that you be no loser. As, if it be meat or drink, though you have no present need, perhaps you will shortly have need, and if you buy not that, you must buy as much of somewhat else. In strict justice you may be a saver, but not a gainer, by buying of the poor in their necessity. 2. But if you buy a durable commodity for less than it is worth, you should take it but as a pledge, and allow the seller liberty to redeem it if he can, that he may get more after of another. 3. And to the poor in such necessity, charity must be exercised as well as justice. Therefore if you are able to lend them money to save them the loss of underselling, you should do it. (I account that man only able who hath money which no greater service of God requireth.) And if you are not able yourself, you should endeavour to get some others to relieve him, if you can without a greater inconvenience.
And for the second case, it is answered before: you may not take more than it is worth, ever the more for another's necessity; nor in any other case than you might have done it in, if there had been no such necessity of his.