As the doctor saw it, too many men took a woman’s lack of sexual satisfaction as evidence of her frigidity, rather than as evidence of their own limitations, outright selfishness, or ignorance. Such men, he wrote, “have no realisation of their deficiencies.” Ideal Marriage’s bluntness about some sexual matters was striking. Van de Velde wrote openly, for example, about whether it was okay to have intercourse during menstruation and during pregnancy, explaining that although caution might be warranted under certain conditions, couples could otherwise go for it. But at its core, his book was a sustained argument that a sizzling sex life is a cornerstone of a happy marriage, and that husbands neglect their role at their peril.