Williamson模態知識論方案（WM）的主張，是在關於構成性事實的知識的協助下，我們可以透過反事實想像來獲得形上學模態知識。然而學界一般認為，構成性事實的知識其實就是形上學模態知識，因此WM有方法論循環的疑慮。Dohrn試圖區分關具有模態型態的命題的知識與知道其模態型態的形上學模態知識，指出我們在反事實想像的運用是前者，而非後者，以此來迴避WM的循環問題。本文試圖論證Dohrn與Williamson的方案有著類似的特徵，因此會出現類似的理論困難，不是無法解決WM的循環問題，就是會讓WM失去模態知識論方面的吸引力。

Williamson’s counterfactual-based modal epistemology (WM) holds that, given the background knowledge of constitutive facts, modal knowledge can be acquired by counterfactual imagination. However, if knowledge of constitutive facts is also a sort of knowledge of metaphysical modality, then WM is prone to the methodological circularity. To parry the circularity problem, Williamson and Dohrn similarly make a distinction between knowledge of a proposition that is necessary and knowledge of the modal status of the proposition. The idea is to sort the knowledge of constitutive facts into the former kind. In this paper, we argue that the Dohrn -Williamson proposal fails to settle the circularity issue of WM, and even if it is granted that the proposal works, it makes WM less attractive as a modal epistemology.