One of the essential elements of a contract is the consent of the parties. This consent must be free, mutual, and communicated by each to the other.
An apparent consent is not real or free if it is obtained through duress, menace, fraud, undue influence, or mistake. Consent is not mutual unless all the parties agree upon the same thing in the same sense.
Consent can be effectively communicated only by some act or omission of the contracting party by which the party intends to communicate consent, or which necessarily tends to communicate consent.