A valid marriage emerges thanks to the founding power of one sole efficient cause—consent. Marriage is a complex human reality; it encompasses physio-biological, psychological, personal, social, religious, moral, and judicial aspects. The essence and characteristics of marriage are determined by natural law. From here, Canon Law made an extraordinary effort, unknown by the other judicial codes, to investigate the natural demands of marriage, just as they are demanded by the dignity of the human being.

Consent is the only efficient cause of the matrimonial bond. It is generally accepted that the mutual consent of both of the contracting parties is what “makes” each marriage specific, not only in an “efficient” sense but also in a “formal” sense, using the scholastic terminology. The celebration of marriage has no effect if consent is lacking. Consent is the sole and irreplaceable cause of marriage, and therefore presupposes and demands natural, absolute and relative capacity of both of the contracting parties.