This seldom happened, and its failure gave rise to the “mother-in-law” joke. One of the purposes of a joke is to prevent thought ?a purpose in which this particular joke was highly successful. No one seemed to realize that a girl brought up to be dependent would naturally be dependent upon her mother, and therefore could not enter into that whole-hearted partnership with a man which is the essence of a happy marriage.
Source: On Education, especially in early childhood, 1926, Pt. 2：Education of character, chap. 11: Affection and Sympathy
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