FAILURE OF CONSIDERATION DISCUSSED. A consideration may apparently be valuable and sufficient, and turn out to be no considera tion at all, or before the contract is executed it may fail. (i Pars. Cont. 462.) If the thing to be done is in its nature separable and divisible, and there is no under standing which makes it entire, the part which fails not going to the essence of the contract, it is good in part, and the failure in part will not destroy the residue. (Lucas v. Godwin, 3 Bing (N. C.) 746.) Some con tracts are by their nature and intent not to be avoided by reason of a slight or immaterial variation of failure in the consideration, as in the sale of lands where a definite number of acres are called for, followed by the words "more or less." A total failure of consideration invalidates the contract, and money paid out on ac count of it may be recovered. But except in case of mistake of fact, money paid voluntarily by a person who knows fully what bargain he is making, cannot be recovered. (i Pars. Cont. 466.) As contract results from agreement, and agreement requires two or more assenting minds, it follows that there must be at least two parties to every contract. The parties to a con tract may be individuals, or aggregations of persons, as corporations, partnerships and the like; they may act for themselves, or represent others as their agents, attorneys, servants, and the like; they may act jointly or severally. But at present we are not concerned' with these distinctions. For the purpose of the forma tion of a valid contract there must be parties capable of contracting, and it is our purpose to find out who are thus capable, or, rather, to find out who are incapable, as all persons are presumed competent to contract, and disability where it exists, must be set up when re lied upon as a defense to a contract.