Journal of the History of Philosophy

Plato, Proclus, and the Limitations of Science S. SAMBURSKY I THE NEOPLATONICREVlV~of Plato's views on the physical world offers some highly interesting aspects to the historian of scientific ideas. There is first of all the interaction between a 600-year-old tradition and other philosophical systems that grew up during this long period and that exerted such a decisive influence on later antiquity. And there is further the magnificent development of science--mathematics and astronomy in particular--in the period following Plato, reaching its climax in the Hellenistic era. This development introduced profound changes in the scientific world picture by adding a wealth of new facts to astronomy, mechanics, optics, and biology, and thus facing the later disciples of Plato with a difficult alternative : They could either assume an orthodox attitude by doubting the facts or at least belittling their significance for the Platonic doctrine; or else they could compromise by attempting to interpret the facts in the Platonic spirit--doing so by availing themselves of the well-known expedient of reading between the lines of the master's writings. It can, of course, not be denied that everything Plato has written on the physical world and on scientific cognition will always be, as it has been in antiquity, subject to interpretations. The task of a Platonic commentator is made even more difficult by his poetic style, his predilection for allegory, and his frequent use of allusions at the very moment when one expects systematic analysis. The increasing anti-metaphysical bias of modern science combined with the fact that Plato himself was neither a practicing scientist nor a creative mathematician led to the disparagement of his contribution to scientific thought in the last centuries. This applies in particular to the Timaeus,where the main tenets of PIato's scientific doctrine are expounded. However, on the whole, this negative attitude is not justified. The consistency and significance of Plato's epistemology of science is borne out by his statements in the Timaeusif they are taken together with his assertions concerning the role of mathematics in the cognition of nature and his appeal to the astronomers to "save the phenomena" of the planetary motions. Careful consideration of all these passages, regarded as a coherent whole, will show in the first place that Plato's philosophy of science does not fall short of his other great contributions to philosophy and human thought. It will further serve as a background against which the significant shift of emphasis that is found in Proclus's evaluation of the capacity of the human mind for the progressive understanding of nature will be seen. We all know of Plato's fundamental belief that the sensible world, i.e., the obiect of physical inquiry, is only an image of the inaccessible world of ideas. The intelligible world, the ultimate reality, is permanent and unchangeable, whereas [11 2 HISTORY OF PHILOSOPHY the material world is a world of transience and change. Every possible description of the physical world is therefore by necessity only a plausible story, not rising above the level of probability. This is the background of the celebrated passage in the Timaeus (29 C) : If then.., we prove unableto render an accountat all points entirely consistentwithitself and exact,you must not be surprised.If we can furnish accountsno less likely than any other, we must be content,rememberingthat I who speak and you my judges are onlyhuman, and consequently it is fittingthat we should, in these matters, accept the likelystory and look for nothingfurther. Here science has once and forever been assigned a place below the absolute truth, in view of the transient nature of the physical world and the role of the sensible world as an image of truth. Can some assertion be made as to the essence of this image? What is the ontological significance of all the changes and transmutations and what is the mechanism of that permanent generative process whose various components blend into the one perceptible unit which we call "nature"? Plato's answer is given in his allegory of the struggle between Reason and Necessity (Timaeus 48 A) : "The generation of this universe was a mixed result of the combination...