Expertise has become a topic of increased interest to philosophers. Fascinating in its own right, expertise also plays a crucial role in several philosophical debates. My aim in this paper is to draw attention to an important, and hitherto unappreciated feature of expertise: its brittleness. Experts are often unable to transfer their proficiency in one domain to other, even intuitively similar domains. Experts are often unable to flexibly respond to changes within their domains. And, even more surprisingly, experts will occasionally (...) be outperformed by novices when confronted with novel circumstances within their domains of expertise. In section 1, I marshal the evidence in favour of brittleness. In section 2, I argue that appeals to brittleness can advance the dialectic in debates on skilled action and provide reasons to reject a powerful recent argument offered by Christensen et al. : 693–719, 2019). In section 3, I appeal to brittleness to argue against a common conception of philosophical expertise, according to which philosophers possess a domain-general set of reasoning skills. Although my argument in this section is largely negative, there is a twist. Recalibrating our understanding of philosophical expertise opens new avenues of research for defenders of the so-called ‘expertise defence’ against the findings of experimental philosophy. (shrink)