We begin this paper by defining and discussing what rationalism and rationality are. We also then debate and discuss the core concepts associated with closely related and allied concepts such as empiricism, positivism and liberalism, and weigh these in in relation to rationality and rationalism. The history of the rationalist movement worldwide, and in India are also explored, and their aims, objectives, mission and goals explored as well. We also review and overview some rationalist groups, and individual rationalists from all over the world, and from all walks of life, and trace their history, and provide their biographies as well wherever necessary. Some schools of thought pertaining to rationality and rationalism are also explored, both in India, and elsewhere in the world. Likewise, the interface of various concepts associated with rationalism and rationality and various strands of social sciences theory are also probed and investigated. Lastly and mostly importantly, we explore various lacunae, deficiencies and shortcomings associated with the rationalist movements worldwide, and propose course-corrections to address them. We expect and anticipate therefore, that this would give the much necessary shot in the arm for the rationalist movement, and make it more effective and efficacious in the context of the twenty-first century. It will also naturally help such movements win and gain people’s trust as well.