Reductive intellectualists about knowledge-how (e.g., Stanley & Williamson Journal of Philosophy 98, 411–44, 2001; Stanley Noûs 45, 207–38, 2011a, 2011b; Brogaard Philosophy Compass 3, 93–118, 2008a, Grazer Philosophische Studien 77, 147–90 2008b, Philosophy and Phenomenological Research 78, 439–67 2009, 2011) hold, contra Ryle (1946, 1949), that knowing how to do something is just a kind of propositional knowledge. In a similar vein, traditional reductivists about understanding-why (e.g., Salmon 1984; Lipton 2004; Woodward 2003; Grimm The British Journal for the Philosophy of Science 57, 515–35, 2006; Greco 2009; Kelp 2014) insist, in accordance with a tradition beginning with Aristotle, that the epistemic standing one attains when one understands why something is so is itself just a kind of propositional knowledge—viz., propositional knowledge of causes. A point that has been granted on both sides of these debates is that if these reductive proposals are right, then knowledge-how and understanding-why should be susceptible to the same extent as knowledge-that is to being undermined by epistemic luck. This paper reports experimental results that test these luck-based predictions. Interestingly, these results suggest a striking (albeit, imperfect) positive correlation between self-reported philosophical expertise and attributions of knowledge-how, understanding-why and knowledge-that which run contrary to reductive proposals. We contextualize these results by showing how they align very well with a particular kind of overarching non-reductive proposal, one that two of the authors have defended elsewhere (e.g., Carter and Pritchard Philosophy and Phenomenological Research 91, 181–99, 2015a, Noûs 49, 440–53, 2015b, Australasian Philosophical Quarterly 93, 799–816, 2015c) according to which knowledge-how and understanding-why, but not knowledge-that, essentially involve cognitive achievement (i.e., cognitive success that is primarily creditable to cognitive ability). We conclude by situating the interpretive narrative advanced within contemporary discussions about the role of expertise in philosophical judgment.