After recalling that the Church has always been opposed to any form of unjust discrimination against persons, based on religion, sex, race, age, etc., the text invites the faithful to consider same-sex marriage as a major form of injustice to all people, an injustice, which, like all the others, the Church can only denounce. In fact, says the letter, it is highly unfair to legitimize the false assertion that there is no difference between man and woman, between a father and a mother. Consequently, it is equally unjust, say the Australian Bishops, to ignore the particular values that real marriage serves; to ignore the importance for children of having, as far as possible, a mum and a dad, committed to them and to each other for the long haul; to destabilize marriage further at a time when it is already under considerable pressure; and to change retrospectively the basis upon which all existing married couples, wanting to say yes forever, got married.

The letter, therefore, touches on the difference between the emotional tie vs. complete one-flesh union; the importance of marriage and family, of fathers and mothers; and, finally, the negative consequences, for society as a whole, resulting from a redefinition of marriage that distorts its natural meaning.