The traditional moral code prohibiting murder, theft, etc., is part of it. The same perennial philosophy, this common inheritance of humanity's common sense, also sees marriage as the foundational unit of society and prohibits those things that directly attack it, like adultery, and also those things that call its purpose and function into question, such as contraception and homosexual relationships. These things call the purpose of marriage into question because, according to the perennial philosophy whether found in the West's Aristotelian Thomism or in China's Confucism, the purpose of marriage is the begetting of children and the mutual benefit of the spouses. Lopping off one of those purposes does not merely leave a sterilized marriage, but a crippled or imitation marriage. You can call it what you like. The pioneers of our present situation called it "companionate marriage," marriage for companionship only. But whatever they called it, it was not marriage according to the perenniel philosophy.
The trick in undermining the perennial philosophy in the West has been that the worst things are saved for last. Nobody came out eighty years ago and said what they wanted for this foundational institution not merely of the West but of all human society. They didn't say that they wanted to see it virtually liquidated. They said they wanted to make it more about love. That sounded real nice, I bet. But they snuck in a concept of love that had chiefly to do with feelings, and was not so much about permanence and the begetting of children. Everything since regarding marriage has been legitimated on the basis of this new, false concept of love - love as a feeling. The problem with feelings isn't that they are bad. They are unstable. And obedience to feelings as if they were gods explains a great deal of the fifty percent divorce rate, for starters.
It's going to be hard for us to transcend our feelings and do what's right even when it doesn't feel good. We won't be able to do it on our own, and as a culture we've gone too far down this road of irresponsibility masquerading as love merely to tweak our course. We need wholesale repentence. Only Jesus can bring it. We who know we need it also need to pray for it. If the Pelosis of the world are leading us into moral oblivion, they will be held accountable. If we who think we know better don't spend hours fervently praying, by our prayers hitting the brakes, we will be held accountable for that.
St. Thomas Aquinas made the bulk of his academic career going around Europe after a man named Sieger of Brabant, who said you could have contradictory truths (not perceptions, but realities), and that whatever you called a thing, that it was. Everywhere St. Thomas went, he calmly tried to get folks to listen to common sense and reason. While he lived, he was very successful because he was very prayerful. Let's follow his example.
St. Thomas Aquinas, pray for us.