The mental capacity to enter into a contract is absolutely necessary to formation of a binding agreement, therefore, inability to exercise the reasoning faculties or to give an intelligent assent to the terms of the contract through insanity or mental deficiency by any of the parties thereto will prevent the formation of a valid contract,13 this is too elementary to require the citation of authority.

Minor v. Brown, 133 N. Y. 308; Hiles v. Fisher, 144 N. Y. 306; Wales v. Coffin (95 Mass), 13 Allen 213; McDermott v. French, 15 N. J. Eq. 48; Bidler v. Robinson, 73 N. J. Eq. 169; Fladung v. Rose, 58 Md. 13.

12. Barton v. Barton, 147 Mich. 318. In the Barton case, for a certain consideration, namely, of agreed payments to be made the wife "surrendered all claims to and right for dower, support, and all claims of every name, nature and description." The husband then died testate and the wife sought to obtain her widow's share of the testator's estate. It was held that the contract being fully executed, followed by a consideration, prevented the wife from enforcing any claim against the husband's estate as his widow. This opinion contains an interesting discussion in which a number of cases are discussed and distinguished. In re. Geannott's Estate, 212 Mich. 442: In this case a contract was executed between the husband and wife in which the following language was used: "And does hereby release all dower rights which she now has or may hereafter have in any property of the said Jos. C Geannott, each of said parties do hereby release any claim which they have or may hereafter have in or to the property of the other." The husband in this case attempted to claim an interest in the estate of Florence Geannott and the court held he could not do so.

13. Elliott On Contracts, Sec. 260.

Capacities to make a contract is the exception and not the general rule, therefore the law presumes that there is a full capacity to contract. Persons entering into an agreement will be presumed to be adults and competent to enter into the contract they have made.14 The incapacity to enter into a contract might be classified under two general heads: they are, natural incapacity, such as insanity or imbecility including drunken persons, and those who are made by operation of the law incapable of entering into the contract, such as infants and married women, at common law. For a full discussion of this subject, which is not peculiar to land contracts, and therefore not fully treated here, the reader is referred to a general work on contracts relating to this subject.15