§7. Further qualifications of the duty of fidelity to promises, the consideration of which is involved in more difficulty and dispute, are suggested when we examine more closely the conditions under which promises are made, and the consequences of executing them. In the first place, it is much disputed how far promises obtained by `fraud or force' are binding. As regards fraud, if the promise was understood to be conditional on the truth of a statement which is found to be false, it is of course not binding, according to the principle I originally laid down. But a promise may be made in consequence of such a fraudulent statement, and yet made quite unconditionally. Even so, if it were clearly understood that it would not have been made but for the false statement, probably most persons would regard it as not binding. But the false statement may be only one consideration among others, and it may be of any degree of weight; and it seems doubtful whether we should feel justified in breaking a promise, because a single fraudulent statement had been a part of the inducement to make it: still more if there has been no explicit assertion, but only a suggestion of what is false: or no falsehood at all, stated or suggested, but only a concealment of material circumstances. We may observe that certain kinds of concealment are treated as legitimate by our law: in most contracts of sale, for example, the law adopts the principle of 'caveat emptor', and does not refuse to enforce the contract because the seller did not disclose defects in the article sold, unless by some words or acts he produced the belief that it was free from such defects. Still, this does not settle the moral question how far a promise is binding if any material concealment is shown to have been used to obtain it. We have also to consider the case in which an erroneous impression has not been wilfully produced, but was either shared by the promisee or produced in some way unintentionally. Perhaps in this last case most would say that the bindingness of the promise is not affected, unless it was expressly conditional. But on all these points Common Sense seems doubtful: and somewhat similar difficulties present themselves when we endeavour to define the obligation of promises partly obtained by some degree of illegal violence and intimidation.