Immanuel Kant is the greatest philosopher of Western Europe, one of the leading thinkers of the Enlightenment, the founder of German classical philosophy, the founder of critical idealism, who made a decisive contribution to the development of the European philosophical tradition. ‘Critique of Practical Reason’ is Immanuel Kant's main ethical treatise, which develops the ideas of his ‘Critique of Pure Reason’ and thoroughly examines the concept of the categorical imperative – the highest principle of morality.