Extract the answer to the question from the following context. Question: How vain was Rousseau? Context: In November 1790, François-Louis-Thibault de Menonville, a member of the National Assembly of France, wrote to Burke, praising Reflections and requesting more "very refreshing mental food" that he could publish. This Burke did in April 1791 when he published A Letter to a Member of the National Assembly. Burke called for external forces to reverse the revolution and included an attack on the late French philosopher Jean-Jacques Rousseau, as being the subject of a personality cult that had developed in revolutionary France. Although Burke conceded that Rousseau sometimes showed "a considerable insight into human nature" he mostly was critical. Although he did not meet Rousseau on his visit to Britain in 1766–7 Burke was a friend of David Hume, with whom Rousseau had stayed. Burke said Rousseau "entertained no principle either to influence of his heart, or to guide his understanding—but vanity"—which he "was possessed to a degree little short of madness". He also cited Rousseau's Confessions as evidence that Rousseau had a life of "obscure and vulgar vices" that was not "chequered, or spotted here and there, with virtues, or even distinguished by a single good action". Burke contrasted Rousseau's theory of universal benevolence and his having sent his children to a foundling hospital: "a lover of his kind, but a hater of his kindred".
possessed to a degree little short of madness