In either case the man is _obliged_ or _bound_ not to hinder those, in whose favour the right is abandoned, from the benefit of it; it is his _duty_ not to make void his own voluntary act, and if he does, it is _injustice_ or _injury_, because he acts now _sine Jure_.
Such conduct Hobbes likens to an intellectual absurdity or self-contradiction.

Voluntary signs to be employed in abandoning a right, are words and actions, separately or together; but in all bonds, the strength comes not from their own nature, but from the fear of evil resulting from their rupture.
He concludes that not all rights are alienable, for the reason that the abandonment, being a voluntary act, must have for its object some good to the person that abandons his right.

A man, for instance, cannot lay down the right to defend his life; to use words or other signs for that purpose, would be to despoil himself of the end--security of life and person--for which those signs were intended.
_Contract_ is the mutual transferring of right, and with this idea he connects a great deal.

First, he distinguishes transference of right to a thing, and transference of the thing itself.

A contract fulfilled by one party, but left on trust to be fulfilled by the other, is called the _Covenant_ of this other, (a distinction he afterwards drops), and leaves room for the keeping or violation of faith.