Quest. XVI. If I say I will give such or such a one this or that, am I bound thereby to do it?
Answ. It is one thing to express your present mind and resolution, without giving away the liberty of changing it; and it is another thing to intend the obliging of yourself to do the thing mentioned. And that obligation is either intended to man, or to God only; and that is either in point of rendition and use, or in point of veracity, or the performance of that moral duty of speaking truth. If you meant no more in saying, I will do it, or I will give it, but that this is your present will, and purpose, and resolution, yea, though it add the confident persuasion that your will shall not change; yet this no further obligeth you than you are obliged to continue in that will; and a man's confident resolutions may be lawfully changed upon sufficient cause. But if you intended to alienate the title to another, or to give him present right, or to oblige yourself for the future to him by that promise; or to oblige yourself to God to do it by way of peremptory assertion, as one that will be guilty of a lie if you perform it not; or if you dedicate the thing to God by those words as a vow; then you are obliged to do accordingly (supposing nothing else to prohibit it).
Quest. XVII. Doth an inward promise of the mind not expressed, oblige?
Answ. In a vow to God it doth; and if you intend it as an assertion obliging you in point of veracity, it doth so oblige you that you must lie. But it is no contract, nor giveth any man a title to what you tacitly thought of.
Quest. XVIII. May I promise an unlawful thing (simply so) without an intention of performing it, to save my life from a thief or persecutor?
Answ. No: because it is a lie, when the tongue agreeth not with the heart. Indeed those that think a lie is no sin when it hurteth not another, may justify this, if that would hold good; but I have before confuted it, part i. in the chapter against lying.
Quest. XIX. May any thing otherwise unlawful become a duty upon a promise to do it?
Answ. This is answered before, part i. chapter of perjury and vows: a thing unlawful will be so still, notwithstanding a vow or promise; and some so of that also which is unlawful antecedently but by accident; as e. g. It is not simply unlawful to cast away a cup of wine or a piece of silver (for it is lawful upon a sufficient cause); but it is unlawful to do it without any sufficient cause. Now suppose I should contract with another that I will do it; am I bound by such a contract? Many say no, because the matter is unlawful though but by accident; and the contract cannot make it lawful. I rather think that I am bound in such a case; but yet that my obligation doth not exclude me wholly from sin; it was a sin before I promised it (or vowed it) to cast away a farthing causelessly. And if I causelessly promised it, I sinned in that promise; but yet there may be cause for the performance: and if I have entangled myself in a necessity of sinning whether I do it or not, I must choose the lesser sin; for that is then my duty. (Though I should have chosen neither as long as I could avoid it.) In a great and hurtful sin I may be obliged rather to break my covenant than to commit it, yet it is hard to say so of every accidental evil: my reasons are, 1. Because the promise or covenant is now an accident to be put into the balance; and may weigh down a lighter accident on the other side (but I know that the great difficulty is to discern which is indeed the preponderating accident).
2. I think if a magistrate command me to do any thing which by a small accident is evil (as to spend an hour in vain, to give a penny in vain, to speak a word which, antecedently, was vain) that I must do it; and that then it is not vain because it manifesteth my obedience (otherwise obedience would be greatly straitened). Therefore my own contract may make it my duty; because I am able to oblige myself as well as a magistrate is. 3. Because covenant-breaking (and perjury) is really a greater sin than speaking a vain word; and my error doth not make it no sin, but only entangles me in a necessity of sinning which way soever I take.
Quest. XX. If a man make a contract to promote the sin of another for a reward, (as a corrupt judge or lawyer, officer or clerk, to promote injustice; or a resetter, to help a thief; or a bawd or whore, for the price of fornication,) may he take the reward, when the sin is committed (suppose it repented of)?