Is Aristotle's Cosmology and Metaphysics Compatible

IS ARISTOTLE’S COSMOLOGY AND METAPHYSICS COMPATIBLE WITH THE CHRISTIAN CONCEPT OF CREATION? Horst Seidl As is well known, Aristotle conceived the cosmos as ungenerated, inde- structible, and without beginning or end. When Christian theologians in the Middle Ages began to use Aristotle’s philosophy his cosmology pre- sented them with a problem, because according to Christian revelation the cosmos has been created by God and will be destroyed at the end of time. Thomas Aquinas sought to overcome this problem in his tractate De Aeternitate Mundi by taking the position that philosophical arguments cannot denitively determine whether the cosmos has a beginning or an end. In the following discussion we shall try to show that Aristotle’s conception of the cosmos not only does not simply contradict the conception of creation but also prepares it and can lead to it. Aristotle’s Doctrine of an Ungenerated and Imperishable Cosmos In De Caelo 1 and 2 Aristotle deals with the material bodies which com- pose the whole cosmos and posits that in contrast to the sublunar world, which is composed by the four elements (earth, water, air and re), the supralunar heavenly spheres consist of a fth element. Let us examine rst Aristotle’s main thought in this treatise. Argument from the Material Nature of the Fifth Element with Its Circular Movement Whereas the four sublunar elements have rectilinear movements upward and downward, the fth element, the so-called ether, is endowed with circular motion. De Caelo 3 determines the properties of the fth element. It is neither light nor heavy, and persists without generation and destruction, as well as without growth and alteration ( 86 horst seidl ),1 because everything which comes to be originates from opposite states or properties, with an under- lying substrate,2 which presupposes contrary movements. The circular movement, however, has no opposite and is continuous without beginning or end, as is explained in chapter 4. In view of the further questions which the Presocratics have already posed as to whether the universe is innite and contains innite worlds, Aristotle argues in chapters 5 through 7 that there is no innite body, and likewise argues in chapters 8 and 9 that there cannot be more than one world or cosmos. The arguments are based on the observation of forced movements against natural movements, on the understanding that heavy bodies’ natural motion is downward and light bodies’ is upward. Thus the natural position of the earth is in the center of the cosmos, and by contrast that of re and the ether is in the uppermost region. If there were more worlds, they should consist of the same elements as our existing world and would have to arrange in the same pattern as our world, which therefore is the only existing one. Argument from the Nature of Time The proof of an ungenerated fth element on the basis of its circular motion is conrmed by the proof that this motion is endless in time. Since time is by denition the measure or number of motion, as explained in Physics 4, Aristototle argued that circular motion, which has no beginning or end, is endless in time, because there is at every instant a prior and a posterior stage. In Metaphysics 12.6 Aristotle likewise argues from the nature of time—which always has for every present instant both a prior and a posterior stage—that there must be an endless movement, as is conrmed by the observation of the circular endless movement of the heaven.3 We must also take up the denition of motion for which time is a property. In Physics 3 Aristotle denes motion as the passage from not being to being or from potential being to actual being (in the different categories). Hence motion is “the act of the potential being as such,” or 1 De Caelo 270a14–15. Quotations from Aristotle’s De Caelo are taken from W.K.C. Guthrie’s ed., On The Heavens, (Cambridge Mass., 1939). 2 See Aristotle’s Physics 1. 3 Metaphysics 1071b3–11..

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