Cal. Civ. Code § 1550 : CALIFORNIA CIVIL CODE — OBLIGATIONS — CONTRACTS — NATURE OF A CONTRACT — DEFINITION — Essential to existence of contract

It is essential to the existence of a contract that there should be:

1. Parties capable of contracting;

2. Their consent;

3. A lawful object; and,

4. A sufficient cause or consideration.

Ca. Civ. Code § 1550

Enacted 1872.