Mental capacity or competence
Black's Law Dictionary · Henry Campbell Black, M.A. · 1910
Black's Law Dictionary
Such a measure of intelligence understanding, memory, and judgment (relative to the particular transaction) as will enable the person to understand the nature and effects of his act.
Eaton v. Eaton, 37 N. J. Law, 113, 18 Am. Rep. 716; Davren v. White, 42 N. J. Eq. 569, 7'Atl. 682; Co.nley v. Nailor, 118 U. S. 127 , 6 Sup. Ct. 1001. 30 L. Ed. 112.