VIII. In all contracts, natural justice requires that there should be an equality of terms: insomuch that the aggrieved party has an action against the other for overreaching him. This equality consists partly in the performance, and partly in the profits of the contract, applying to all the previous arrangements, and to the essential consequences of the agreement. IX. As to an equality of terms previous to the contract, it is evident that a seller is bound to discover to a purchaser any defects, which are known to him, in a thing offered for sale; a rule not only established by civil laws, but strictly conformable to natural justice. For the words of agreement between contracting parties are even stronger than those, on which society is founded. And in this manner may be explained the observation of Diogenes the Babylonian, who in discussing this topic said, it is not every degree of silence, which amounts to concealment; nor is one person bound to disclose every thing, which may be of service to another. Thus for instance, a man of science is not strictly bound to communicate to another that knowledge, which might redound to his advantage. For contracts, which were invented to promote a beneficial intercourse among mankind, require some closer and more intimate connection than bare good-will to enforce their obligation. Upon which Ambrose has justly remarked, "that, in contracts, the faults of things exposed to sale ought to be made known, of which unless the seller has given intimation, though he may have transferred the right of property by sale, yet he is liable to an action of fraud."