In discussing the mental representations of animals of different grades of intelligence, Sextus shows a very good comprehension of the philogenetic development of the organs of sense, and draws the final conclusion that external objects are regarded differently by animals, according to their difference in constitution.[1] These differences in the ideas which different animals have of the same objects are demonstrated by their different tastes, as the things desired by some are fatal to others.[2] The practical illustrations given of this result show a familiarity with natural history, and cognizance of the tastes and habits of many animals,[3] but were probably few of them original with Sextus, unless perhaps in their application; that this train of reasoning was the common property of the Sceptic School, we know from the fact that Diogenes begins his exposition of the first Trope in a way similar to that of Sextus.[4] His illustrations are, however, few and meagre compared with those of Sextus, and the scientific facts used by both of them may mostly be found in other authors of antiquity given in a similar way.[5] The logical result of the reasoning used to explain the first Trope, is that we cannot compare the ideas of the animals with each other, nor with our own; nor can we prove that our ideas are more trustworthy than those of the animals.[6] As therefore an examination of ideas is impossible, any decided opinion about their trustworthiness is also impossible, and this Trope leads to the suspension of judgment regarding external objects, or to [Greek: epoche.][7] [1] _Hyp._. I. 54. [2] _Hyp._. I. 55. [3] _Hyp._. I. 55-59. [4] Diog. IX. 11, 79-80. [5] Pappenheim _Erlauterung Pyrr. Grundzuege Par_. 41. [6] _Hyp_. I. 59. [7] _Hyp_. I. 61. After reaching this conclusion, Sextus introduces a long chapter to prove that animals can reason. There is no reference to this in Diogenes, but there is other testimony to show that it was a favourite line of argument with the Sceptics.[1] Sextus, however, says that his course of reasoning is different from that of most of the Sceptics on the subject,[2] as they usually applied their arguments to all animals, while he selected only one, namely the dog.[3] This chapter is full of sarcastic attacks on the Dogmatics, and contains the special allusion to the Stoics as the greatest opponents of the Sceptics, which has been before referred to.[4]