Pascal, later on, repeated that extreme intelligence was very near to extreme madness, and himself offered an example of it. Diderot wrote: “I conjecture that these men of sombre and melancholy temperament only owed that extraordinary and almost Divine penetration which they possessed at intervals, and which led them to ideas, sometimes so mad and sometimes so sublime, to a periodical derangement of the organism. They then believed themselves inspired, and were insane. Their attacks were preceded by a kind of brutish apathy, which they regarded as the natural condition of fallen man. Lifted out of this lethargy by the tumult within them, they imagined that it was Divinity, which came down to visit and exercise them.... Oh! how near are genius and madness! Those whom heaven has branded for evil or for good are more or less subject to these symptoms; they reveal them more or less frequently, more or less violently. Men imprison them and chain them, or raise statues to them.”[9] Many examples of men who were at once mad and highly intelligent were offered by Hécart in his _Stultitiana, ou petite bibliographie des Fous de Valenciennes, par un homme en démence_; by Delepierre, an enthusiastic bibliophile, in his curious _Histoire littéraire des Fous_ (1860); by Forgues, in _Revue de Paris_ (1826); and by an anonymous writer in _Sketches of Bedlam_ (London, 1873). On the other hand, it was shown in Lélut’s _Démon de Socrate_ (1836) and _Amulette de Pascal_ (1846), in Verga’s _Lipemania del Tasso_ (1850) and in my own _Pazzia di Cardano_ (1856), that there are men of genius who have long been subject to hallucinations, and even to monomania. Other proofs, the more precious because impartial, were supplied by Réveillé-Parise, in his _Physiologie et Hygiène des hommes livrés aux travaux de l’esprit_ (1856). Moreau (de Tours), who delighted in the least verisimilar aspects of truth, in his solid monograph, _Psychologie Morbide_ (1859), and J. A. Schilling, in his _Psychiatrische Briefe_ (1863), endeavoured to show, by researches that were very copious although not very strict in method, that genius is always a neurosis, and often a true insanity. Hagen has more recently sought to prove a thesis which is partly the same in his _Verwandtschaft des Genies mit dem Irrsinn_ (Berlin, 1877), and, indirectly, Jürgen-Meyer, in his admirable monograph, _Genie und Talent_ (from the _Zeitschrift für Völker-psychologie_, 1879). These two writers have tried to explain the physiology of genius, and, singularly, they have reached conclusions which were reached, more by intuition than through close observation, by an Italian Jesuit, now quite forgotten--Bettinelli--in his book, _Dell’ entusiasmo nelle belle Arti_ (Milan, 1769). Radestock, in his _Genie und Wahnsinn_ (Breslau, 1884), added little to the solution of the problem, as he merely copied, for the most part, from his predecessors, without profiting greatly by their work.