 As in ours, many in Aquinas’ milieu found it difficult to understand how mutually agreeable sex could be a serious moral issue, or indeed a moral issue at all. Aquinas noted this, but was clear that every kind of conduct that acts out and thus confirms and reinforces a disposition of will contra bonum matrimonii is seriously wrong because so many aspects of individual and social flourishing profoundly depend upon the health of the institution of marriage, as it exists in the real lives of adults and children. It is worth repeating, since the point is so often misunderstood and misreported, that Aquinas’ moral arguments for distinguishing good from bad sex never run from “natural” to “therefore good/reasonable/right”, but always from “good/reasonable/right” to therefore “natural” (and similarly, of course, for unreasonable and unnatural): see II-II q. 153 a. 2c, a. 3c, q. 154 a. 1c, a. 2 ad 2, a. 11.