Question IV: Of how many kinds is the price of things

SALES, and purchases are just or unjust chiefly by reason of the price.

NOW the just price is twofold. One is fixed by public law, as when a pound of flesh, a jar of oil, or a measure of wine is sold for so much. This price consists in an indivisible sum, and is called by Aristotle, first Ethics, chapter 7, the legal price, which the Doctors commonly follow. The other is the natural price, which is imposed by nature itself according to prudent estimation. That this is just appears from the law pretium, ff. ad Legem Falcidiam. This price, however, does not consist in an indivisible sum, because it depends on many circumstances, on which see Nauar. cap. 23. num. 79. Medina C. de restis. quaest. 31. Couar. l. 2. var. cap. 3. In it, therefore, there is a certain latitude, within which justice is not violated, as D. Bonau. in speculo animae, cap. 2. Molina T. 2. disp. 347. Less. l. 1. cap. 21. dub. 2. num. 8. Fagundez l 5. de contract. cap. 29. Caspens. Tract. 19. sect. 2. Tanner. disp. 4. quaest. 7. num. 27. teaches.

HENCE the natural price is threefold. The highest, or rigorous; the middle, or moderate; and the lowest, or charitable. For example, let the middle price be one hundred; the rigorous will be 105; the lowest will be 95. Again, let the middle be 10; the lowest 8; the highest 12. Such examples are given by Couar. l. 2. var. cap. 3. Lessius, and Molina above, Caspensis num. 7. who, however, computing the accrescence in the hundred, holds that in tens it is increased only by five, and decreased only by one and a half.

WITHIN the limits of these three prices there cannot be injustice, so that a thing may be sold dearer on credit than for cash in hand, provided one keeps within these bounds. So it is gathered from D. Thom. 2. 2. quaest. 77. art. 1. Caietano there, Molina t. 1. disp. 347. Less. l. 2. cap. 21. dub. 2. num. 11. Soto l. 6. de iust. quaest. 2. art. 3. Couar. l. 2. var. cap. 3. Scoto in 4. dist. 15. quaest. 2. Maiore quaest. 29. and 40. Conrado de contract. cap. 3. quaest. 56. Nauar. in C. qualitas, de poenis. disp. 5. num. 43. Fagundez l. 5. cap. 29. Casp. num. 7. who, however, with others notes that the price must be determinate. Wherefore, if you sell on this condition: I sell for whatever you wish, it is invalid.