孟德爾究竟發現了什麼？一個實驗發現的典型模式

What did Gregor Mendel Discover? On a Typical Pattern of Experimental Discovery

古典遺傳學之父孟德爾，一向被遺傳學家、教科書、生物史家認為「發現」了古典（孟德爾）遺傳學定律。近來一些科史家宣稱，孟德爾並未發現「孟德爾遺傳學定律」。若是如此，孟德爾本人究竟發現了什麼？他對科學的貢獻何在？要回答這兩個問題，必須重新訴說孟德爾的實驗與古典遺傳學起源的整個科學歷史，也必須考察「科學發現」的哲學問題。目前流行的兩種科學史觀，大致也可以套用到孟德爾和古典遺傳學的故事上。證據史觀流行在科學家、生物學家與遺傳學家之間，它是一種發現、除錯、累積與進步的歷史圖像，它主張孟德爾當然發現了孟德爾遺傳定律，這是孟德爾對科學的偉大貢獻。孔恩式的典範史觀主張孟德爾的工作屬於雜交育種學的老傳統，他的實驗目的不在於遺傳，更沒有發現孟德爾定律。孟德爾時代的遺傳觀念被一個發育論典範支配，以孟德爾定律為基礎的古典遺傳學，則是一個全新的典範。本文指出典範史觀比證據史觀更能合理交代複雜的遺傳學發展史，但它似乎忽略了雜交育種的實驗傳統。本文認為在典範史觀的故事上，補充一個「模型基礎的實驗發現」觀點，就能更合理交代孟德爾的實驗在古典遺傳學歷史中的位置。本文也展示了孟德爾的發現故事，體現一個「實驗發現」的典型模式，並企圖界定這種實驗發現模式的基本特徵。

Gregor Mendel, the famous nineteenth-century Austrian botanist, has been considered the discoverer of laws of classical (Mendelian) genetics. Several historians of biology recently began to argue that Mendel had never discovered Mendel’s laws. If he did not discover Mendel’s laws at all, what is his discovery? What is his contribution to science? To answer the above questions, one has to re-examine the whole story of his experimentation and the origin of classical genetics. The philosophical problems involved in scientific discoveries have also to be reconsidered. By and large, two current but different views of historiography have been applied to write the history of Mendel’s discovery and the origin of classical genetics. The evidence-based historiography sees the history of science as a process filled by discoveries of novel theories and facts, exclusion of errors, and accumulation and progress of knowledge. It holds that Mendel did discover Mendel’s laws. The discovery is therefore his greatest contribution to science. In contrast, Kuhnian paradigm-based historiography attributes Mendel’s works to an old experimental tradition of breeding and hybridization. It claims that Mendel’s experiment was not about heredity and he was not a Mendelian himself. In addition, most ideas about heredity in Mendel’s time were dominated by the developmentalist paradigm. The classical genetics based on Mendel’s laws is a new paradigm entirely different from developmentalism. In this study, I argue that the paradigm-based historiography provides a better explanation of the history of genetics than its evidence-based rival. Yet, as it seems to neglect the independent role played by experimentation, the paradigm-based version of Mendel’s experimental work is not adequate. To give a more plausible account of the place of Mendel’s experiment in the history of genetics, I develop a model-based concept of experimental discovery and demonstrate that Mendel’s achievement embodies a typical pattern of experimental discovery.