The debate about homosexual "marriage" comes down to the purpose of marriage. If the purpose of marriage is "to attach mothers and fathers to their children and to one another," then there is a relevant dissimilarity between heterosexual couples and homosexual couples with regard to marriage; and that means that the principle of equality (justice) does not require equal treatment. Justice requires that likes be treated alike and unlikes differently, in proportion to their differences. See here for an illuminating essay by Jennifer Roback Morse.
Homosexual “Marriage”
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