形上學會探究關於存在與實在的問題，而形上學家時常會爭辯著某類東西是否存在，或某類現象是否是實在的。然而，這些爭辯常常會顯得十分像是在雞同鴨講。例如，當「組成虛無論」（mereological nihilism）否認桌子椅子的存在，卻不反對日常語言中關於桌子椅子的宣稱，我們似乎會覺得他們只是把「存在」用了和中文「存在」很不一樣的字義。又例如，當「不相容論」（incompatibilism）與「相容論」（compatibilism）在爭辯自由意志與決定論是否相容時，我們似乎也覺得他們只是擁有著不同的「自由」概念而已。但若是如此，這些形上學爭辯就不會是關於客觀實在的「實質爭議」（substantial issues），而只不過是關於我們的字詞與概念的「字面之爭」（verbal issues）。但果真如此嗎？

就算形上學爭辯真的是實質之爭，我們又要如何確定誰對誰錯呢？如果形上學爭辯只是關於我們字詞與概念的字面之爭，那麼似乎使用傳統的「概念分析」（conceptual analysis）或「語言分析」（linguistic analysis）便足夠了。但如果形上學爭辯是關於客觀實在的實質爭議，那麼我們似乎需要更進一步的方法論工具來進行形上學研究。但這樣的工具會是什麼呢？也許是透過某種「形上解釋」（metaphysical explanation）或「立基」（grounding）的想法，顯明實在的層層結構來探討最基礎的東西是什麼。也許是透過某種「形上語意」（metaphysical semantics）或「結構」（structure）的想法，提供一套更好的、切中要理的（joint-carving）概念學（ideology）來描述最基礎的實在。又或許是透過某種「形上律則」（metaphysical law）或「本質」（essence）的想法，掌握住比模態必然性更細緻的連結來跨越基礎與非基礎間的解釋鴻溝。

最近的這十年來，這類的「後設形上學」議題突然受到了廣大的注目和討論。本課程的目標之一，便是要介紹這些後設形上學議題的發展與討論。本課程將選用Metametaphysics: New Essays on the Foundations of Ontology (Oxford, 2009) 為主要的閱讀材料，逐一探討後設形上學中主要的立場與爭辯。

Metaphysics asks questions about existence and reality, debating whether certain alleged entities exist, or whether certain alleged phenomena are real. But sometimes these debates seem like talking past each other. For instance, when the mereological nihilist denies the existence of chairs and tables without really questioning our ordinary claims about chairs and tables, they just seem to use the word ‘existence’ in a radically different meaning from our ordinary English words. Similarly, when the incompatibilist and the compatibilist disagree about whether free will is compatible with determinism, they just seem to have different conceptions of freedom. But if so, they would not be genuine substantial debates about objective reality, but simply verbal issues about our words and concepts. Is it really so?

Even if we have good reason to think metaphysical debates are substantial, how are we supposed to settle them? If they are merely verbal debates about our words and concepts, perhaps conceptual analysis and/or linguistic analysis will do. But if they are substantial debates about objective reality, we require some further methodological tools to help us investigate them. What can such tools be? Perhaps it is the idea of metaphysical explanation or grounding, which reveals to us a layered reality for investigating what is the fundamental. Perhaps it is the idea of metaphysical semantics or structure, which provides us with some better, joint-carving ideology for describing the fundamental reality. Or perhaps it is the idea of metaphysical law or essence, which gives us more fine-grained connections than brute necessities for bridging the explanatory gaps between the fundamental and the non-fundamental.

The last decade has witnessed a tremendous interest in such metametaphysical questions. This course will provide a critical introduction to them. We will be studying the book Metametaphysics: New Essays on the Foundations of Ontology (Oxford, 2009), which collects a lot of ground-breaking classical papers in this field.