因果關係是否存在程度差異？

Abstract

因果關係是否存在程度差異？對於實際結果，一個因素可以「更是個原因」嗎？無論是在日常語境、自然科學、歷史研究或法律領域中，關於因果關係的宣稱往往涉及因果程度的概念，其判斷更是實質影響著道德責任與決策選擇。然而，傳統上將因果關係視為一種全有或全無的二值關係，並不存在程度上的差異。本文旨在探究與辯護因果關係的程度概念，針對當前因果程度主張面臨的內部困難與外部挑戰，一方面分析並整合因果程度論者分歧的觀點，以建構一組一致的因果程度理論假設，填補當前討論缺乏明確共識的不足；另一方面針對 Sartorio (2020) 提出之判準問題及其反對論證，運用前述理論資源，從三個回應進路辯護因果程度主張。首先，提出因果維度上可通約作為因果貢獻可比較性之條件，並藉由確立判準排序原則以明確界定，唯在反映因果維度上不可通約時，不同因素的因果貢獻方無法比較，從而闡明判準問題之衝突屬於不可比較的案例。再者，論證因果程度理論應符合兩項限制，由此篩選出結果一致的合理因果程度判準，進而解消判準問題。此外，本文亦質疑比例性原則在因果程度論辯中的核心地位，論證 Sartorio 的攻擊其實僅反對比例性原則，駁斥其攻擊會對因果程度主張構成威脅。有鑑於因果程度論者存在三種可行回應進路，本文論證判準問題並非因果程度理論無解的難題，因果程度主張尚未出現決定性的反對論證。故而，因果程度確實是可合理支持且應進一步探索的重要議題，提供因果程度判準亦為因果關係研究的重要任務之一。

Does causation come in degrees? Can a factor be “more of a cause” than others for a given outcome? The concept of degrees of causation is pervasive in causal claims across everyday, scientific, historical, and legal contexts, influencing moral responsibility and decision-making through evaluating causal contributions. However, causation has traditionally been viewed as an all-or-nothing relation, denying the concept of causal degrees. This paper investigates and defends the concept of degrees of causation. To address two challenges, I synthesize divergent views among proponents, constructing consistent assumptions for the ongoing debate. Drawing on this framework, I respond to Sartorio's (2020) problem of criteria through three approaches. First, I propose commensurability across causal dimensions for comparing contributions, along with a criterion-ranking principle. These show contributions are incomparable only when reflecting incommensurability, clarifying that conflicts within the problem of criteria are instances of incomparability. Second, I argue that theories of causal degrees must satisfy two constraints that help resolve the problem of criteria by selecting consistent and reasonable criteria. Third, I challenge the central role of the proportionality principle in the debate, arguing that Sartorio's argument merely targets it, posing no threat to the claim of causal degrees. Given these responses, the problem of criteria is far from unsolvable, and there is no decisive refutation of the claim that causation comes in degrees. Therefore, the concept of causation in degrees warrants further exploration, with the establishment of such criteria as a primary task in causal studies.