What does it take for a belief to count as knowledge rather than lucky guesswork? Explaining Knowledge develops a new answer, in favor of an “abductivist” theory of knowledge. According to abductivism, a belief constitutes knowledge when, given the way it is formed or maintained, the best explanation of its being true rather than false lies in the facts themselves rather than in adventitious factors. Sven Bernecker here develops the abductivist theory and argues for its superiority by contrasting it with its two main rivals: safety theory and causal explanationism. To situate these competing theories, safety theorists maintain that a belief counts as knowledge only if it could not easily have been false, emphasizing modal robustness, while causal explanationists insist that knowledge requires the right kind of causal connection---often a direct explanatory chain---between fact and belief. Both approaches capture important insights, but each faces longstanding difficulties in accounting for environmental luck, mathematical knowledge, knowledge based on false premises, and lottery cases.Bernecker posits that the abductivist theory of knowledge is superior to its competitors because it can handle a wider range of test cases and offers greater explanatory power-notably, unlike causal explanationism, it can handle barn cases and account for mathematical knowledge. By focusing on the explanatory relationship between a belief's truth and the facts that make it true, abductivism outperforms the safety theory in terms of accounting for the knowledge-undermining role of misleading evidence, and in distinguishing Gettier cases from knowledge of falsehoods and Frankfurt-style knowledge.Explaining Knowledge shows that the abductivist model offers fresh solutions to well-known philosophical puzzles about luck, mistaken assumptions, and mathematical knowledge, while also explaining how new evidence can undermine what we previously took ourselves to know.