One of the earliest references to what a promisor was to have for his undertaking was in the action of assumpsit.
The natural question is, what the promisor was to have for his promise.
When form and intention concurred the promisor must answer for what he undertook.
It is only in the degree of power possessed by the promisor over the event.
The second stage was when the doctrine of consideration was introduced in its earlier form of a benefit to the promisor.
In short it is a benefit to the promisor, or a detriment to the promisee.
A promise in certain words has a definite meaning, which the promisor is presumed to understand.
A mutual promise, no matter how slight or trivial, or the payment of anything valuable to the promisor, is sufficient.
The person to whom the offer was made paid $1000 for the promise, therefore the promisor is bound to keep it.
A promisor may be a surety, a guarantor, or an indorser of a negotiable instrument.