無數定律中的自然類：一個最簡的反休謨式自然形上學框架

Abstract

本文基於反休謨式觀點及純粹形上學考量提出一套關於自然類與自然定律的共同理論。透過闡釋自然類實在論之論旨，本文指出自然類是可僅參照可作為獨立於心智之分類標準的事實而對諸個物劃分出的類。在一般性的反休謨式的形上架構裡，可作為獨立於心智之分類標準的事實只有受轄於定律這種事實，因為是定律使因果成為可能，且定律之於自然齊一性的奠基是不可或缺的。因此，有何等自然類端視有何等定律，而有何等定律要看定律本身如何個別化。定律是存有物，各自的本性是單純的且只能功能性地刻畫，其個別化是固有的但標誌在互相之間功能刻畫的不同。藉由考量因果的本性，本文論證定律是最定性且是局部全包的，因為因果亦是如此。本文接者展示幾類重要的非定性或非因果通則的非偶性都能完全奠基在最定性的因果律之上，並於過程中論證定律是歷時性的、層級全包並且無視層級的。鑒此，我們只需要承認歷時性因果定律這單一一類定律的存在。基於定律是最定性且是局部全包的，以及自然類之受轄於定律的觀念，自然類結果是最定性的完整性質叢類，而此事並不需要我們承認有作為存有物的自然類。一個最簡的反休謨式自然形上學框架故而只需要設置定律，且是單一一類定律，來作為所有非邏輯非概念性模態的來源，但不需要設置自然類，其實在性完全倚賴作為存有物的定律的實在性。然而，雖然定律能為歸納的可靠性提供基礎，自然類並沒有任何知識論上的功用。整體來說，定律和自然類都不是知識的對象，只有不對應到單一定律的通則和非自然類才是。

This study advances a joint theory of natural kinds and laws from purely metaphysical considerations and from the anti-Humean vantage point. By explicating the thesis of natural kind realism, natural kinds are shown to be kinds into which objects could be classified by reference to mind-independent facts alone which may function as mind-independent membership criterion. It is asserted that the only plausible such facts in a generic anti-Humean metaphysical framework are facts of law-governance, as the posit of laws is what makes genuine causality possible and is indispensable for grounding uniformities of nature. What natural kinds there are then depends on what laws there are, which in turn depends on how laws are individuated. It is shown that laws are ontic items whose individual nature is simple and only functionally characterisable, and whose individuation is inherent but is marked by any and only the difference in their characterisation. By considering the nature of causality, it is argued that laws are maximally determinate and locally comprehensive because, and in the sense that, causality is so. In showing that several important classes of determinable and noncausal generalities may be fully grounded in maximally determinate causal laws alone for their non-accidentalness, it is also demonstrated that laws and causality are diachronic, level-comprehensive and level-indifferent. Thus, only one sort of laws need be posited, which are all causal and, hence, diachronic. Given the maximal determinateness and local comprehensiveness of laws, and given the law-governance conception of natural kinds, natural kinds turn out to be maximally determinate full cluster-types, which do not demand the posit of ontic items which are natural kinds as such. A minimalist anti-Humean metaphysical framework should then have a posit of laws, of just one single sort, at its core, which are sources of all non-logical and non-conceptual modalities, and no posit of natural kinds, whose reality consists solely in that of ontically real laws. However, while laws may be said to provide grounds for inductive reliability, natural kinds have no epistemological role. In general, neither laws nor natural kinds are epistemic targets; only non-lawful generalities and non-natural kinds are.