根據其他可能性原則（PAP），行動者S對其實際上的行動Φ有道德責任，僅當S可以不做Φ。Harry G. Frankfurt（1969）藉由法蘭克福式案例（FSCs）來論證PAP有反例，所以並不成立。不過，Philip Swenson（2015 & 2016）提出了「無原則差別」論證來辯護PAP：他首先指出「直覺上某些不作為的FSCs中的行動者明顯沒有責任」，然後他進一步論證「不作為的FSCs與一般的FSCs沒有原則上的差別」，由此結論「一般FSCs中的行動者也同樣沒有責任」。對此，Florian Cova（2017）提供責任歸屬的兩個條件：「展現條件」與「解釋條件」，並以此說明不作為的FSCs與典型的FSCs在道德責任歸屬上的實質區別。如果這兩條件成立，那Swenson的「無原則差別」論證就很難算是真正地辯護了PAP。本文論證，「展現條件」有適用性問題、合法性問題、以及解釋上的困境，而「解釋條件」則缺乏了恰當的理論基礎，因此Cova對Swenson的批評並不成立。

According to the Principle of Alternative Possibilities (PAP), an agent is morally responsible for what she has done only if she could have done otherwise. Harry G. Frankfurt (1969) presents the Frankfurt-style cases (FSCs) as counterexamples to the PAP, and argues that PAP is therefore false. However, Philip Swenson (2015, 2016) has recently proposed the “No Principled Difference Argument” (NPDA) to defend PAP. Firstly, he claims that our intuitive reaction to FSCs is that an agent may not be responsible for omitting to act, i.e. omission in the Frankfurt-style cases (OCs). Then, he argues that there is no principled distinction between FSCs and OCs. Thus, the agents in FSCs, likewise, may not be responsible for their actions. In response to Swenson’s view, Florian Cova (2017) rejects NPDA by appealing to two principles of responsibility ascription—the performance condition and the explanation condition—and explicates the significant differences of moral responsibility between FSCs and OCs. If the two conditions proposed by Cova were true, Swenson’s NPDA would fail to defend PAP. Nonetheless, this paper argues that the performance condition is confronted with problems of applicability and legitimacy, as well as explanatory dilemma, while the explanation condition lacks an appropriate theoretical foundation. Therefore, Cova’s objections to NPDA remain untenable.