In this paper I present, and offer a solution to, a heretofore unacknowledged textual puzzle that arises from Margaret Cavendish's use of inconceivability to make claims about what is metaphysically impossible. On the one hand, Cavendish asserts that objects or events she cannot conceive of are impossible in nature (i.e., inconceivability entails impossibility in nature). On the other hand, she writes that there are some things that exist or occur in nature that are inconceivable to humans (i.e., inconceivability does not entail impossibility in nature). Put simply, Cavendish seemingly contradicts herself. This textual puzzle not only threatens to undermine Cavendish's philosophical method; it also calls her opposition to human exceptionalism into question. By asserting that what is inconceivable to her is impossible in nature, Cavendish implies by contraposition that she can conceive of everything that is metaphysically possible. In so doing, she seems to make an exception at least for herself: though she believes that other parts of nature cannot conceive of everything in nature, she implies that she can. Ultimately, I argue that Cavendish thinks we can sometimes tell why something is inconceivable. In some cases, something is inconceivable because it lies beyond the limits of humans' mental capacities. In other cases, something is inconceivable because it is contradictory. This interpretation solves the textual puzzle, as it is consistent for Cavendish to maintain that some objects and events in nature are beyond our mental limits and that we can derive the impossibility of some object or event in nature from its contradictoriness. My interpretation preserves Cavendish's opposition to human exceptionalism, moreover, as no part of nature can conceive of contradictions. That is, Cavendish's claim is not merely that what is inconceivable to her is impossible in nature, but rather that what is inconceivable to her and to every other part of nature is impossible in nature. / Master of Arts / Margaret Cavendish, a seventeenth century philosopher, makes two seemingly contradictory claims throughout her philosophical works. On the one hand, she implies that if something is inconceivable to her — that is, if she cannot form a mental picture of it — that thing is impossible in nature. On the other hand, she writes that there are plenty of things that exist or occur in nature which are inconceivable to humans. A textual puzzle therefore arises: Cavendish seems to simultaneously maintain (1) that something is impossible in nature if she cannot conceive of it, and (2) that something is not necessarily impossible in nature if she cannot conceive of it. In this paper, I propose that Cavendish believes humans can at least sometimes determine why something is inconceivable. That is, we can at least sometimes diagnose our inability to form a mental picture of something. In some cases, Cavendish thinks, we cannot form a mental picture of something because of our limited, human mental capacities. (We might think, for example, that this is why we cannot form a mental picture of all the colors butterflies see.) In other cases, we cannot form a mental picture of something because that thing is contradictory. (We might think, for instance, that this is why we cannot form a mental picture of an apple that is both red all over and not red all over.) I further argue that Cavendish only asserts that something is impossible in nature if it is inconceivable because it is contradictory. On my account, the textual puzzle I presented above is in fact not so puzzling. Cavendish thinks that if something is inconceivable because it is contradictory, then it is impossible in nature. She also thinks that there are plenty of things in nature that we cannot conceive of because of our limited human mental capacities. Thankfully, these two claims are not in tension.