ART. 1390. - The following contracts are voidable or annullable, even though there may have been no damage to the contracting parties:
(1) Those where one of the parties is incapable of giving consent to a contract;
(2) Those where the consent is vitiated by mistake, violence, intimidation, undue influence or fraud.

These contracts are binding, unless they are annulled by a proper action in court. They are susceptible of ratification.

⁸ ART. 1327. - The following cannot give consent to a contract:

x x x

(2) Insane or demented persons, and deaf-mutes who do not know how to write.

⁹ Bordalba v. Court of Appeals, G.R. No. 112443, January 25, 2002, p. 7.

¹⁰ ART. 1318. There is no contract unless the following requisites concur:
(1) Consent of the contracting parties;
(2) Object certain which is the subject matter of the contract;
(3) Cause of the obligation which is established.
¹¹ ART. 1409. The following contracts are inexistent and void from the beginning:

(1) Those whose cause, object or purpose is contrary to law, morals, good customs, public order or public policy;

(2) Those which are absolutely simulated or fictitious;
(3) Those whose cause or object did not exist at the time of the transaction;
(4) Those whose object is outside the commerce of man;
(5) Those which contemplate an impossible service;

(6) Those where the intention of the parties relative to the principal object of the contract cannot be ascertained;

(7) Those expressly prohibited or declared by law.

These contracts cannot be ratified. Neither can the right to set up the defense of illegality be waived.

¹² Civil Code, Art. 1390. The following contracts are voidable or annullable, even though there may have been no damage to the contracting parties:

(1) Those where one of the parties is incapable of giving consent to a contract;
. . .

These contracts are binding, unless they are annulled by a proper action in court. They are susceptible of ratification.

¹³ Metropolitan Waterworks and Sewerage System (MWSS) vs. Court of Appeals, 297 SCRA 287, 307 (1998).