We find here in the Sceptical School, shortly after the time of Aenesidemus, the same tendency to dogmatic teaching that--so far as the dim and shadowy history of the last years of the New Academy can be unravelled, and the separation of Pyrrhonism can be understood, at the time that the Academy passed over into eclecticism--was one of the causes of that separation. It is true that the Tropes of Agrippa show great progress in the development of thought. They furnish an organisation of the School far superior to what went before, placing the reasoning on the firm basis of the laws of logic, and simplifying the amount of material to be used. In a certain sense Saisset is correct in saying that Agrippa contributed more than any other in completing the organisation of Scepticism,[1] but it is not correct when we consider the true spirit of Scepticism with which the Tropes of Agrippa were not in harmony. It was through the very progress shown in the production of these Tropes that the school finally lost the strength of its position. Not content with having reduced the number of the Tropes from ten to five, others tried to limit the number still further to two.[2] Sextus gives us no hint of the authorship of the two Tropes. Ritter attributes them to Menodotus and his followers, and Zeller agrees with that opinion,[3] while Saisset thinks that Agrippa was also the author of these,[4] which is a strange theory to propound, as some of the material of the five is repeated in the two, and the same man could certainly not appear as an advocate of five, and at the same time of two Tropes. [1] Saisset _Op. cit._ p. 237. [2] _Hyp._ I. 178. [3] Zeller III. 38; Ritter IV. 277. [4] Saisset _Op. cit._ p. 231. The two Tropes are founded on the principle that anything must be known through itself or through something else. It cannot be known through itself, because of the discord existing between all things of the senses and intellect, nor can it be known through something else, as then either the _regressus in infinitum_ or the _circulus in probando_ follow.[1] Diogenes Laertius does not refer to these two Tropes. In regard to all these Tropes of the suspension of judgment, Sextus has well remarked in his introduction to them, that they are included in the eighth, or that of relation.[2] [1] _Hyp._ I. 178-179. [2] _Hyp._ I. 39. _The Tropes of Aetiology_. The eight Tropes against causality belong chronologically before the five Tropes of Agrippa, in the history of the development of sceptical thought. They have a much closer connection with the spirit of Scepticism than the Tropes of Agrippa, including, as they do, the fundamental thought of Pyrrhonism, _i.e._, that the phenomena do not reveal the unknown.