A novel epistemology of science contends that good science need not attain its aims, but it must justify its claims.   In Heart of Science, philosopher Jacob Stegenga breaks with the most dominant epistemologies of science to argue that in judging scientific activity, we should focus on its justification, not the achievement of truth or knowledge. Yet, Stegenga argues, the aim of science goes far beyond justification and is, instead, a special kind of truth—common knowledge, a broadly shared and mutually justified scientific finding.   Drawing on both historical examples and recent events like the COVID-19 pandemic, Stegenga outlines his approach before delving into its implications for scientific evaluation, testimony, values, progress, and credit, as well as the nature of science during times of crisis. Truth, he shows, may not be easily identified in the short term. However, an evaluation of scientific justification, grounded in shared standards, is possible. This framework helps us appraise—and appreciate—historical theories that ultimately weren’t accurate and offers fresh insights about appropriate science communication and public trust in scientific research. Justification and scientific rigor are not just means to an end, Stegenga writes, but the very heart of good science.   Ambitious, authoritative, and accessible, Heart of Science offers a new vision for the philosophy of science.