Douthat explains the notion of Open Marriage as a blend between (gay) conservative and liberationist views of marriage. Here we would see it as a logical outgrowth of the Lockeanization of marriage. Aspects of marriage like sexual complimentarity and child care duties are dismantled in light of the ‘free individual and nothing more.’ This is the idea behind Justice Kennedy’s mystery passage in Casey and which he reiterates in Lawrence v. Texas: “At the heart of liberty is the right to define one's own concept of existence, of meaning, of the universe, and of the mystery of human life.”
In a follow-up post, Douthat argues this individualist understanding will allow manliness to run amok. Monogamy was a way of civilizing or domesticating the thumos of males. Autonomy in principle will yield to a contest of wills in practice, with an unruly male spiritedness coming out ahead. Liberation indeed.
Finally, it is interesting to see Savage defend Open Marriage on the grounds of NATURE, albeit through a Modern rather than a Classical or Christian lens. He thinks we are not ‘wired for monogamy.’ For Savage, the good is natural and nature is identified with our instinctive and spontaneous inclinations. This is in contrast to the pre-modern view which found rationality and teleology (purpose) in nature. At the moment this view is unpopular, but Savage’s proposal to return to nature might allow this older understanding to return-however much he has wrong, at least he has the starting point right.