ESSENTIALS OF THE DEFINI TION. The essential things to be considered in every contract are: The agreement, the parties, the consid eration, and the subject matter, or the thing to be done or omitted. (Fuller v. Kemp, 138 N. Y. 231.) The agreement, or assent of the parties to the terms of the contract, need not be a union of the two minds, but simply a union of the manifest thoughts or pur pose of the contracting parties. So in implied con tracts, we shall see that this assent is conclusively pre sumed to exist as to all such features as the judge or legal expert thinks reasonable to the situation and surroundings of the parties. The consideration is the reward or inducement which engages one or the other to enter into the contract. The parties must be two or more in number and competent to contract. The sub ject matter of the contract may be as varied as the ne cessities of human life; so that it is the few things dis allowed as subjects of contract that are to be men tioned, and not those that are allowed. Each of these essential elements will receive attention in the subse quent sections.