§ 72. We now come to the consideration of the competency of parties to contract. The general principle of law is, that all persons not rendered incompetent by personal disability, or by considerations of public policy, may be parties to a contract.
§ 73. Incompetency to contract is of two kinds: 1st, Natural; and 2d, Legal. The former of these classes subdivides itself naturally into the contracts of: first, Lunatics and Idiots; secondly, Drunkards. Lord Coke enumerates four different classes of persons, who are deemed in law to be non compotes mentis. The first is an idiot or fool natural; the second is he who was of good and sound memory, and by the visitation of God has lost it; the third is a lunatic, lunati-cus, qui gaudet in lucidis intervallis, and sometimes is of good and sound memory, and sometimes non compos mentis; and the fourth is a non compos mentis by his own act, as a drunkard.1 No contract can exist, unless there be a mutual consent of the parties, and an intelligent understanding of its termsj and accordingly the first incapacity, recognized by the law, arises whenever the mental infirmity of either party, or of both parties, precludes the possibility of a just apprehension of the terms of the agreement, or of an intelligent assent to them.2