Karl Leonhard Reinhold was an Austrian philosopher who helped to popularise the work of Immanuel Kant in the late 18th century. His "elementary philosophy" (Elementarphilosophie) also influenced German idealism, notably Johann Gottlieb Fichte, as a critical system grounded in a fundamental first principle.

Immanuel Kant was a German philosopher and one of the central Enlightenment thinkers. Born in Königsberg, Kant's comprehensive and systematic works in epistemology, metaphysics, ethics, and aesthetics have made him one of the most influential and controversial figures in modern Western philosophy, being called the "father of modern ethics", the "father of modern aesthetics", and for bringing together rationalism and empiricism earned the title of "father of modern philosophy".