原因和本質：克普勒與伽利略科學思想的形上學差異

Causation and Essence: The Discrepancies in Metaphysics of Scientific Thoughts Between Kepler and Galileo

本文有兩重目的，一是提供克普勒與伽利略兩人疏離關係一個另類解釋，二是透過兩人思想差異的耙梳，呈現十七世紀初期科學變遷中，擁護相同理論的科學家彼此觀點的歧異，及其引領思潮的衝突與調和。克普勒和伽利略都是哥白尼學說的支持者，有過短暫交流，但科學見解少有交集，甚至觀點針鋒相對。為何如此？這問題吸引許多學者提出各種說法。本文從兩人形上學觀點差異的角度，尤其原因和本質的觀念，說明兩人關係的疏離的原因。另一方面，經由這種思想差異的分析，展示兩人各自支持哥白尼理論的不同想法，及十七世紀初科學哲學思潮的衝突與整合的來龍去脈。本文依序從問題背景、克普勒的天文學工作、行星軌道形狀、潮汐等主題，論述兩人科學思想的形上學差異。

The aim of this paper is twofold. First, it offers an alternative explanation for the distant relationship between Kepler and Galileo through revealing their divergent ways of philosophizing. It shows the two Copernicans had their own metaphysical ideas, especially concerning their notions of causation and of essence which differed from each other. Without disclosing the differences in their metaphysical ideas, it is hard to understand why the two Copernicans were never able to work closely together. Second, by way of examining both men, it also illustrates that Kepler and Galileo embraced conflicting schools of thought which were in existence before the seventeenth century. The reconciliation of these schools including Platonism and Aristotelianism, essentialism and nonessentialism, animism and mechanism, with Copernican astronomy was an important part of Kepler and Galileo’s work in the early seventeenth century now known as the scientific revolution.