This book gathers together 28 personal stories told by leading thinkers and practitioners in conservation – all of whom have something to say about the uncomfortable tension that arises when data meet dogma. Together, they make a powerful argument for conservation science that measures effectiveness and evolves in response to new data, rather than clinging to its treasured foundational ideas. Several chapters raise doubts about some of conservation’s core tenets, including the notion that habitat fragmentation is bad for biodiversity, biodiversity declines are threatening ecosystem function, non-native species are a net negative for conservation, and fisheries management is failing. Another set of chapters warns of the potent power of conservation narratives: undeniably useful to inspire conservation action, but potentially dangerous in locking in thinking against contrary data. These chapters challenge iconic stories about GM crops, orangutans in oil palm forests, frog feminization, salmon versus dams, rehabilitating oiled otters, and wolves in Yellowstone. A final set of chapters addresses conceptual and methodological approaches such as environmental tipping points, global assessments, payment for ecosystem service programs, and working with corporations. Throughout, examples of confirmation bias emerge—not as dishonesty, but as a human foible that is a challenge for all science, not just conservation science. Graduate students, in particular, will find a wealth of ideas to inspire their own research. Each chapter points to additional data that could help resolve lingering debates and improve conservation effectiveness.