Consent in contract of sale

A contract is void if one of the essential requisites of contracts under Article 1318 of the New Civil Code is lacking. Article 1318 provides:
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.
All these elements must be present to constitute a valid contract. Consent is essential to the existence of a contract; and where it is wanting, the contract is non-existent. In a contract of sale, its perfection is consummated at the moment there is a meeting of the minds upon the thing that is the object of the contract and upon the price. Consent is manifested by the meeting of the offer and the acceptance of the thing and the cause, which are to constitute the contract. To enter into a valid contract of sale, the parties must have the capacity to do so. Every person is presumed to be capacitated to enter into a contract until satisfactory proof to the contrary is presented.(Vitalista v. Perez, G.R. No. 164147, 16 June 2006). The burden of proof is on the individual asserting a lack of capacity to contract, and this burden has been characterized as requiring for its satisfaction clear and convincing evidence.