Science is the great intellectual adventure, but can also be an instrument of profit, power, and privilege. Wrongly used, it might yet make the twenty-first century our last. To make sense of this, we need to let go of old ideas and assumptions. This No-Nonsense Guide to Science introduces a new way of thinking about science, moving away from ideas of perfect certainty and objectivity. We must accept uncertainty and ignorance in the field, as well as the need for citizens’ participation in the policies involving science.