(21) Marriage is therefore a stable, joint project that comes from the free and total self-giving of fruitful conjugal love as something due in justice.  Since an original social institution is founded (and which gives origin to society), the dimension of justice is inherent in conjugality itself. “They are free to celebrate marriage, after having chosen each other with equal freedom, but as soon as they perform this act, they establish a personal state in which love becomes something that is owed, entailing effects of a juridical nature as well”.[34][34]  Other ways of living sexuality can exist—even against natural tendencies-, other forms of living together, other friendly relationships –whether based or not on the sexual difference-, and other ways of bringing children into the world. But what is specific about the family based on marriage is that it is the only institution that incorporates and unites all the elements mentioned at the same time and in an original way.