But if that prove impossible afterwards, which before was thought possible, the Covenant is valid, and bindeth, (though not to the thing it selfe,) yet to the value; or, if that also be impossible, to the unfeigned endeavour of performing as much as is possible; for to more no man can be obliged.
Covenants How Made Voyd Men are freed of their Covenants two wayes; by Performing; or by being Forgiven.

For Performance, is the naturall end of obligation; and Forgivenesse, the restitution of liberty; as being a retransferring of that Right, in which the obligation consisted.
Covenants Extorted By Feare Are Valide Covenants entred into by fear, in the condition of meer Nature, are obligatory.

For example, if I Covenant to pay a ransome, or service for my life, to an enemy; I am bound by it.

For it is a Contract, wherein one receiveth the benefit of life; the other is to receive mony, or service for it; and consequently, where no other Law (as in the condition, of meer Nature) forbiddeth the performance, the Covenant is valid.

Therefore Prisoners of warre, if trusted with the payment of their Ransome, are obliged to pay it; And if a weaker Prince, make a disadvantageous peace with a stronger, for feare; he is bound to keep it; unlesse (as hath been sayd before) there ariseth some new, and just cause of feare, to renew the war.