Much of Kant's intellectual energy, throughout his long career, was devoted to issues in the philosophy of natural science. Kant was not a “philosopher of science” in the sense now familiar within the Anglo-American tradition – a specialist focused on the nature and methods of scientific inquiry, say, or on the foundations of some particular science, such as physics or biology. Kant was a generalist philosopher in the classical sense, concerned with all human thought as such (both practical and theoretical) and with the structure and character of all distinctively human activities and institutions (science, art, religion, law, morality, politics, and so on). Natural science, however, was a particularly central and important example of human thought. Indeed, for the eighteenth century as a whole, the age of Enlightenment and the triumph of Newtonianism, the recent culmination of the scientific revolution of the sixteenth and seventeenth centuries in the work of Newton had elevated natural science to previously undreamt of heights within the intellectual firmament. Thinkers as diverse as Voltaire, Hume, and Kant himself all took the Newtonian achievement in natural science as a model of the human intellect at its best, and as a model, more specifically, for their own philosophical activity.
In the eighteenth century, in fact, philosophy as a discipline had not yet clearly split off from natural science, as is indicated by the circumstance that what is now called “natural science” was still often called “natural philosophy” at the time.