Most nations acknowledge that marriage is a relationship which provides dignity, purity and sanctity

Marriage is an exclusive heterosexual activity and can never apply to any other relationship

Marriage is a legally protected relationship and is the most highly preferred relationship in law

The union of two consenting adults of different genders is unique with unlimited value to society

The relationship between two persons of the same sex is fundamentally different than the heterosexual relationship in marriage

Marriage is a public status and has been reserved exclusively for special covenant heterosexual unions because they are uniquely beneficial to society.

Committed marriage benefits both society and individuals by :-
Heterosexual behavior is uniquely moral, dignified, decent and pure
Sexual intimacy for adults that is safe
Procreation of children in love and family security
Enhanced childrearing with both male and female role models
Improved status of women through security
Improved status of men through morality
A contract between equals
Strength and security of family, is not isolated individuals
Family integrity underpinning of society
Enhanced civic virtue
Enhanced public morality
Government efficiency and economies through functioning families
International acceptance of laws and martial status
Superior health outcomes for spouses and children
A seed ground for democracy and self government
Enhanced intergenerational transmission of knowledge and skills

Marriage is preferred because society accepts heterosexual behavior is preferred over homosexual (or other) behavior