There is some shew of reason in the opinion of those who, without taking into consideration the power of the civil law to annul or diminish an obligation, maintain that a person is bound to fulfil a promise which he has given under impressions of fear. For even in this case there was CONSENT, though it was extorted; neither was it conditional, as in erroneous promises, but absolute. It is called CONSENT. For as Aristotle has observed, those who consent to throw their goods overboard in a storm, would have saved them, had it not been for the fear of shipwreck. But they freely part with them considering all the circumstances of time and place. VIII. To render a promise valid, it must be such as it is in the power of the promiser to perform. For which reason no promises to do illegal acts are valid; because no one either has, or ever can have a right to do them. But a promise, as was said before, derives all its force from the right of the promiser to make it, nor can it extend beyond that. If a thing is not now in the power of the promiser, but may be so at some future time; the obligation will remain in suspense. For the promise was only made under the expectation of some future ability to fulfil it. But if a person has a controul over the condition upon which the promise is made, to realise it or not, he lies under a moral obligation to use every endeavour to fulfil it. But in obligations of this kind also, the civil law, from obvious motives of general utility, occasionally interposes its authority to make them void: obligations, which the law of nature would have confirmed. IX. The next general inquiry, for the most part, refers to the validity of promises made upon any immoral or unlawful consideration; as if, for instance, any thing is promised to another on condition of his committing a murder. Here the very promise itself is wicked and unlawful, because it encourages the commission of a crime. But it does not follow every FOOLISH or IMPROVIDENT promise loses the force of an obligation, as in the confirmation of imprudent or prodigal grants, for no further evil can result from a confirmation of what has been already given: and the invalidity of promises would be a greater evil than any that could result from a confirmation of the most improvident. But in promises made upon IMMORAL and UNLAWFUL considerations, there is always a criminality remaining, even while they continue unfulfilled. For during the whole of that time, the expectation of fulfilment carries with it the indelible mark of encouragement to the commission of a crime.