行動哲學中的一個核心爭論是關於意圖進行某個行動或達成某個目標是否蘊含相信自己將會實現它。認知主義者肯定此觀點，而非認知主義者則反對。本篇論文在「恆毅力」的脈絡下為認知主義辯護——「恆毅力」是指行動者儘管面對重大逆境，仍堅持追求一個長期目標。我主張，一個意圖達成此類長期目標且具有恆毅力的行動者，可以相信她將成功實現該目標。當然，儘管存在來自逆境的重大反對證據，仍然相信自己會成功，這在知識論上看似乎是不理性的。為了解決這個問題，我支持「實踐信念」的主張，該主張說明了具有毅力的行動者如何在面對反對證據時，仍能理性地相信自己會成功。這個解釋為認知主義提供了一條途徑，使其能夠同時容納恆毅力中所展現出的知識理性與實踐理性。

A central debate in the philosophy of action concerns whether intending an action or goal entails believing that one will achieve it. Cognitivists affirm this view, while non-cognitivists reject it. This thesis defends cognitivism within the context of grit, where an agent persists in pursuing a long-term goal despite significant adversity. I argue that a gritty agent who intends such a long-term goal can believe that she will succeed in achieving the goal. Of course, believing in her success despite significant counterevidence from the difficulties appears epistemically irrational. To address this, I endorse an account of practical belief that explains how the gritty agent can rationally believe in success despite counterevidence. This account offers cognitivism a way to accommodate both the epistemic and practical rationality of grit.