Marriage is often thought to be the culmination of a romantic relationship. The most intimate form of love bears itself out by yearning for a union that reflects the weight of that intimacy. As such, marriage can be adequately understood as the commitment of psychological and sexual union between two human beings for the span of their lifetime. As romantic love develops in two lovers, it guides them towards a bond of intimacy that is the most significant of any among human relations—that is, marriage so defined.

But what is this psychosexual union that romantic love seeks? Alexander Pruss, Associate Professor of Philosophy at Baylor University, suggests that sexual union is a matched and cooperating physical union with an aim towards the same goal (e.g., reproduction).[1] For example, a person’s heart is not united with the arteries in virtue of their being attached (or even permanently attached) to each other, but they are united insofar as they are cooperating towards the same goal.[2] So the sexual union is one not only of physical connection but of physiological striving. Psychological union, it seems, could likewise be understood as a matched and cooperating state of intentionality towards the same goal. This combination of psychological and sexual cooperation sets the stage for a marriage union.

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This understanding of marriage leads to a question: what persons meet the criteria to enter into such a union? Psychologically speaking, to commit one’s lifelong intentions with another person’s, seems to presuppose a mental faculty that has developed the ability to do so. As such, undeveloped persons or those with the inability to align their will or intentions could not be thought to enter into such a commitment. Sexually speaking, to commit to a physical union with another person entails the ability to do so. True sexual union is only possible when the sex act involves parts striving toward the same end. This understanding precludes persons whose biological connection does not cooperate in a goal-oriented way.

A possible concern regarding this understanding might be the question of those who are biologically damaged or inhibited—would they be unable to enter into this marriage union? The key to interpreting the psychological and sexual union is found in understanding intention coupled with potentiality. It is when the psychological and physical intention is absent that the marriage union cannot be realized. Those who are unable to physically unite due to a medical condition or some other external factor—their bodies still strive for a cooperative goal, even if that goal is inaccessible. This differs from an attempted sexual union by (say) two persons of the same sex. Such persons’ bodies do not and could not have the physical intention and cooperation required by the sexual union—their bodies do not strive toward a cooperative goal.

This argument would suggest that a marriage union can only be the culmination of persons who (1) have the capacity to unite their will with another person, and (2) have the capacity to unite physically with another person (“to unite” meaning to join together in a cooperative way). This understanding implies that the “marriage” union excludes certain types of relationships. Homosexual couples and people with undeveloped mental faculties (for example) would be unable to enter into the marriage union under the terms stated.

Some might object and call into question this particular definition of marriage. Why think that marriage implies this sort of cooperative intention—both psychologically and physically? But it’s hard to understand “marriage” as uniquely significant by any other defining conditions. Should we think of marriage as a psychological union only? This seems clearly mistaken. Family members, business partners, and friends can all unite their wills toward a common goal without being thought of as the climax of relational intimacy. Likewise, should sexual union alone be the terms for marriage? This also seems to be a shortfall. Casual and non-romantic sex seems to be a modern-day, societal norm. Additionally, victims of sexual abuse and assault are easily recognizable cases of a physical union that are an utter violation of intimacy, not its fulfillment.

It seems plausible, then, that the best understanding of a marriage relationship—a relationship that is the culmination of human intimacy, is one of both psychological and physical union.

[1] “Dr. Alexander Pruss: What Is Sexual Union?,” YouTube, uploaded July 17, 2013,

[2] Pruss,