Arthur Schopenhauer on tetragamy

Was any major philosopher better than Schopenhauer at starting with genuine insight and turning it into an untenable conclusion?

Tetragamy adjusted marriage into an institution that would make life better for men and women, Schopenhauer theorized, because it accommodated the natural sexual and reproductive capacities of humans in ways in which monogamy did not.  It also addressed the material and financial needs of all parties in a more rational way.  Two young men should marry a young woman, and when she outgrew her reproductive ability, and thereby lost her attractiveness to her husbands, the two men should marry another young woman who would "last until the two young men were old."  The financial advantage of this type of marriage would be considerable, Schopenhauer thought.  At first, when the two young men's incomes were low, they would only have to support one woman and her small children.  Later, when their wealth increased, they would have the means to support two women and many children…Schopenhauer never published his musings on tetragamy…

That is from David E. Cartwright's recent Schopenhauer: A Biography.