Our book addresses the role of hypothetical thinking in the formulation and development of scientific theoriestheory construction/development and modelsmodels from a pluralistic point of view, having in mind the outstanding scientific contribution of Copernicus. We begin by discussing the Copernican inspirations for this volume. We then discuss methodological aspects of hypotheses in science, followed by twentieth century insights about the nature and role of hypotheses in science, and then briefly consider hypotheses from a logical point of view. Finally, we provide summaries of each chapter. The various contributors to this edited collection provide a pluralistic picture of the detection, explanation, and use of hypothetical reasoning in the sciences by combining philosophical, historical and methodological analyses. This book not only addresses why hypotheses are so important but also offers insight into how they work within various scientific contexts.