[235] That Carneades was the first to start this difficulty cannot be directly proved, but is conjectured with great probability by Zeller (op. cit., p. 504).
[236] Sext. Pyrrh. Hyp., II., 186. Adv. Math., VIII., 463.
[237] Pyrrh. Hyp., II., 195, 204.
[238] Cicero, De Nat. Deor., I., xxiii., 62; III., iv., 11; xvi., 42; xxi., 53.
[239] Sext., Adv. Math., IX., 182-3.
[240] Cic., De Nat. Deor., III., xviii., 47.
[241] Cic., Acad., II., xxxviii., 120; Zeller, op. cit., p. 506.
[242] Cic., Acad., ibid., 121; Zeller, op. cit., p. 507.
[243] Cic., De Nat. Deor., III., x., 24.
[244] ibid., III., xi., 27.