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.
The Sceptics did not deny the phenomena, but they denied that the phenomena are signs capable of being interpreted, or of revealing the reality of causes. It is impossible by a research of the signs to find out the unknown, or the explanation of things, as the Stoics and Epicureans claim. The theory of Aenesidemus which lies at the foundation of his eight Tropes against aetiology, is given to us by Photius as follows: «There are no visible signs of the unknown, and those who believe in its existence are the victims of a vain illusion.» This statement of Aenesidemus is confirmed by a fuller explanation of it given later on by Sextus. If phenomena are not signs of the unknown there is no causality, and a refutation of causality is a proof of the impossibility of science, as all science is the science of causes, the power of studying causes from effects, or as Sextus calls them, phenomena.
It is very noticeable to any one who reads the refutation of causality by Aenesidemus, as given by Sextus, that there is no reference to the strongest argument of modern Scepticism, since the time of Hume, against causality, namely that the origin of the idea of causality cannot be so accounted for as to justify our relying upon it as a form of cognition.
Myriob. 170 B. 12.
Adv. Math. VIII. 207.
Hyp. I. 180-186.
Ueberweg Op. cit. p. 217.
The eight Tropes are directed against the possibility of knowledge of nature, which Aenesidemus contested against in all his Tropes, the ten as well as the eight. They are written from a materialistic standpoint. These Tropes are given with illustrations by Fabricius as follows:
I. Since aetiology in general refers to things that are unseen, it does not give testimony that is incontestable in regard to phenomena. For example, the Pythagoreans explain the distance of the planets by a musical proportion.
II. From many equally plausible reasons which might be given for the same thing, one only is arbitrarily chosen, as some explain the inundation of the Nile by a fall of snow at its source, while there could be other causes, as rain, or wind, or the action of the sun.
III. Things take place in an orderly manner, but the causes presented do not show any order, as for example, the motion of the stars is explained by their mutual pressure, which does not take into account the order that reigns among them.
IV. The unseen things are supposed to take place in the same way as phenomena, as vision is explained in the same way as the appearance of images in a dark room.
V. Most philosophers present theories of aetiology which agree with their own individual hypotheses about the elements, but not with common and accepted ideas, as to explain the world by atoms like Epicurus, by homoeomeriae like Anaxagoras, or by matter and form like Aristotle.
VI. Theories are accepted which agree with individual hypotheses, and others equally probable are passed by, as Aristotle’s explanation of comets, that they are a collection of vapors near the earth, because that coincided with his theory of the universe.
VII. Theories of aetiology are presented which conflict not only with individual hypotheses, but also with phenomena, as to admit like Epicurus an inclination or desire of the soul, which was incompatible with the necessity which he advocated.
VIII. The inscrutable is explained by things equally inscrutable, as the rising of sap in plants is explained by the attraction of a sponge for water, a fact contested by some.
Hyp. I. 98.
Hyp. I. 180-186; Fabricius, Cap. XVII. 180 z.
Diogenes does not mention these Tropes in this form, but he gives a resumé of the general arguments of the Sceptics against aetiology, which has less in common with the eight Tropes of Aenesidemus, than with the presentation of the subject by Sextus later, when he multiplies his proofs exceedingly to show μηδὲν εἶναι αἴτιον. Although the Tropes of Aenesidemus have a dialectic rather than an objective character, it would not seem that he made the distinction, which is so prominent with Sextus, between the signs ὑπομνηστικά and ἐνδειτικά, especially as Diogenes sums up his argument on the subject with the general assertion, Σημεῖον οὐκ εἶναι,and proceeds to introduce the logical consequence of the denial of aetiology. The summing up of the Tropes of Aenesidemus is given as follows, in the Hypotyposes, by Sextus:—»A cause in harmony with all the sects of philosophy, and with Scepticism, and with phenomena, is perhaps not possible, for the phenomena and the unknown altogether disagree.»
It is interesting to remark in connection with the seventh of these Tropes, that Aenesidemus asserts that causality has only a subjective value, which from his materialistic standpoint was an argument against its real existence, and the same argument is used by Kant to prove that causality is a necessary condition of thought.
Chaignet characterises the Tropes of Aenesidemus as false and sophistical, but as Maccoll has well said, they are remarkable for their judicious and strong criticism, and are directed against the false method of observing facts through the light of preconceived opinion. They have, however, a stronger critical side than sceptical, and show the positive tendency of the thought of Aenesidemus.
Diog. IX. 11, 96-98.
Hyp. III. 24-28.
Adv. Math. VIII. 151.
Diog. IX. 11, 96.
Hyp. I. 185.
Compare Maccoll Op. cit. p. 77.
Chaignet Op. cit. 507.
Maccoll Op. cit. p. 88.