We all swim in a sea of Big Data, dangerously vulnerable to the unscientific thinking that now replaces the critical faculties we used to rely on. We seek simple explanations where complexity is required. But as we endeavor to solve global problems of energy, food, and water shortages, a planetary biodiversity crisis, and emerging threats to our public health, the development of scientific habits of mind becomes even more essential for our survival. We fear numbers and prefer neat and simple solutions to complex problems, but scientific reasoning plays a central role in combating misinformation and is one of our best tools for meeting the upcoming crises of our century. From confronting our fear of quantitative reasoning and demystifying graphs to elucidating the key concepts of probability and data analysis and the use of precise language and logic, this book supplies an essential set of apps for the frontal cortex while making science both accessible and entertaining. Who says it has to be dull to learn to think like a scientist? Who says only a few can do it? Not David Helfand, one of our nation's leading astronomers and science educators. Helfand has taught scientific habits of mind to generations of Columbia University undergraduates, where he continues to wage a provocative and necessary battle against sloppy thinking and the encroachment of misinformation.