Immanuel Kant (; 22 April 1724 12 February 1804) was an 18th-century German philosopher from the Prussian city of Königsberg (now Kaliningrad, Russia). He is regarded as one of the most influential thinkers of modern Europe and of the late Enlightenment.
Kant created a new widespread perspective in philosophy which influenced philosophy through the 21st Century. He also published important works of epistemology, as well as works relevant to religion, law and history. His most important work is the Critique of Pure Reason, an investigation into the limitations and structure of reason itself. It encompasses an attack on traditional metaphysics and epistemology, and highlights Kant's own contribution to these areas. The other main works of his maturity are the Critique of Practical Reason, which concentrates on ethics, and the Critique of Judgment, which investigates aesthetics and teleology.
Pursuing metaphysics involves asking questions about the ultimate nature of reality. Kant suggested that metaphysics can be reformed through epistemology. He suggested that by understanding the sources and limits of human knowledge we can ask fruitful metaphysical questions. He asked if an object can be known to have certain properties prior to the experience of that object. He concluded that all objects that the mind can think about must conform to its manner of thought. Therefore if the mind can think only in terms of causality which he concluded that it does then we can know prior to experiencing them that all objects we experience must either be a cause or an effect. However, it follows from this that it is possible that there are objects of such a nature that the mind cannot think of them, and so the principle of causality, for instance, cannot be applied outside of experience: hence we cannot know, for example, whether the world always existed or if it had a cause. And so the grand questions of speculative metaphysics are off limits, but the sciences are firmly grounded in laws of the mind.
Kant believed himself to be creating a compromise between the empiricists and the rationalists. The empiricists believed that knowledge is acquired through experience alone, but the rationalists maintained that such knowledge is open to Cartesian doubt and that reason alone provides us with knowledge. Kant argues, however, that using reason without applying it to experience will only lead to illusions, while experience will be purely subjective without first being subsumed under pure reason.
Kant’s thought was very influential in Germany during his lifetime, moving philosophy beyond the debate between the rationalists and empiricists. The philosophers Fichte, Schelling, Hegel and Schopenhauer each saw themselves as correcting and expanding the Kantian system, thus bringing about various forms of German idealism. Kant continues to be a major influence on philosophy to this day, influencing both Analytic and Continental philosophy.