Nearly all success is due to some mix of ability and luck. But some successes we attribute to the agent's ability, whereas others we attribute to luck. To better understand the criteria distinguishing credit from luck, we conducted a series of four studies on knowledge attributions. Knowledge is an achievement that involves reaching the truth. But many factors affecting the truth are beyond our control, and reaching the truth is often partly due to luck. Which sorts of luck are compatible with knowledge? We found that knowledge attributions are highly sensitive to lucky events that change the explanation for why a belief is true. By contrast, knowledge attributions are surprisingly insensitive to lucky events that threaten, but ultimately fail to change the explanation for why a belief is true. These results shed light on our concept of knowledge, help explain apparent inconsistencies in prior work on knowledge attributions, and constitute progress toward a general understanding of the relation between success and luck.

and others have demonstrated the surprising fact that the valence of a side-effect action can affect intuitions about whether that action was performed intentionally. Here we report the results of an experiment that extends these findings by testing for an analogous effect regarding knowledge attributions. Our results suggest that subjects are less likely to find that an agent knows an action will bring about a side-effect when the effect is good than when it is bad. It is further argued that these findings, while preliminary, have important implications for recent debates within epistemology about the relationship between knowledge and action.

In epistemology, fake-barn thought experiments are often taken to be intuitively clear cases in which a justified true belief does not qualify as knowledge. We report a study designed to determine whether members of the general public share this intuition. The data suggest that while participants are less inclined to attribute knowledge in fake-barn cases than in unproblematic cases of knowledge, they nonetheless do attribute knowledge to protagonists in fake-barn cases. Moreover, the intuition that fake-barn cases do count as knowledge is negatively correlated with age; older participants are less likely than younger participants to attribute knowledge in fake-barn cases. We also found that increasing the number of defeaters (fakes) does not decrease the inclination to attribute knowledge.

It is often thought that judgments about what we ought to do are limited by judgments about what we can do, or that “ought implies can.” We conducted eight experiments to test the link between a range of moral requirements and abilities in ordinary moral evaluations. Moral obligations were repeatedly attributed in tandem with inability, regardless of the type (Experiments 1–3), temporal duration (Experiment 5), or scope (Experiment 6) of inability. This pattern was consistently observed using a variety of moral vocabulary to probe moral judgments and was insensitive to different levels of seriousness for the consequences of inaction (Experiment 4). Judgments about moral obligation were no different for individuals who can or cannot perform physical actions, and these judgments differed from evaluations of a non-moral obligation (Experiment 7). Together these results demonstrate that commonsense morality rejects the “ought implies can” principle for moral requirements, and that judgments about moral obligation are made independently of considerations about ability. By contrast, judgments of blame were highly sensitive to considerations about ability (Experiment 8), which suggests that commonsense morality might accept a “blame implies can” principle.