Wikipedia:
According to his Confessions, before she moved in with him, Thérèse bore him a son and as many as four other children (there is no independent verification for this number[8]). Rousseau wrote that he persuaded Thérèse to give each of the newborns up to a foundling hospital, for the sake of her "honor". "Her mother, who feared the inconvenience of a brat, came to my aid, and she [Thérèse] allowed herself to be overcome" (Confessions). In his letter to Madame de Francueil in 1751, he first pretended that he wasn't rich enough to raise his children but in book IX of the confessions, he gave the true reasons of his choice : " I trembled at the thought of intrusting them to a family ill brought up, to be still worse educated. The risk of the education of the foundling hospital was much less."
Ten years later, Rousseau made inquiries about the fate of his son, but no record could be found. When Rousseau subsequently became celebrated as a theorist of education and child-rearing, his abandonment of his children was used by his critics, including Voltaire and Edmund Burke, as the basis for ad hominem attacks.
Even stranger:
In an irony of fate, Rousseau's later injunction to women to breastfeed their own babies (as had previously been recommended by the French natural scientist Buffon), probably saved the lives of thousands of infants.
