Big questions for party-goer

This book is the first full-length biography of Immanuel Kant in 50 years and, while complicated, is accessible to the general reader.

In 1724, Emanuel Kandt was born in Konigsberg, the capital of East Prussia, to a middle-class family who followed Pietism, a Protestant movement that stressed feelings and action. He received a good moral upbringing from his family but a harsh and unsatisfying education from the local Pietistic school.

At 16, Kant entered the University of Königsberg. He was a bright but defiant student - instead of writing a traditional Latin dissertation, which would advance his career, he wrote a very independent German thesis. He then worked for several years as a private tutor.

Kant, at age 30, returned to the university to complete teacher training and worked as a lecturer, typically teaching 22 hours a week. His thinking then was pre-critical: he based ethics on moral feelings, based belief in God on a metaphysical proof and accepted the usual Christian doctrines. He was a socialite, dressing elegantly and going to parties. Later, he became more serious - his goal was to find the "big picture" that would fit together reason and sensation, knowledge and scepticism, German rationalism and British empiricism.

At 45, Kant became professor of logic and metaphysics at Konigsberg. His inaugural dissertation announced his critical agenda, which he pursued for several years while publishing little.

His Critique of Pure Reason was published when he was 57, and he soon added other works that express the Kantian system that we know and love (or hate). The central theme is that sensing and judging have an a priori structure that has legitimate use only when combined with sensation; so it is sophistical to reason from a priori concepts (such as cause and effect) to conclusions that lie beyond possible experience. Thus we cannot prove free will, God or the afterlife, but we cannot disprove them, so they remain possible objects of faith.

Kant's Foundations of the Metaphysics of Morals claims that the central moral principle is a priori. We are to act only on a maxim that we can will to be universal law; equivalently, we are to treat each rational being as an end, and not simply as a means. His Critique of Practical Reason argues that morality requires belief in free will, God and the afterlife. As Kant's fame spread, he became the focus of sometimes bitter controversies.

While Kant defended belief in God, he stressed that religion was to be based on morality, not morality on religion. His religion involved morality and reason, not churches and bibles. Later he lost belief in God and the afterlife, though how this happened is not clearly spelt out.

I would have preferred less detail on minor figures and more lucid explanation of Kant's earlier views, but these are minor complaints. By the time Kant died in 1804, after years of physical and mental decline, his thought was out of fashion. Nevertheless, his writings have had great influence, not by giving us a watertight system for our acceptance, but by providing clues about how to work out our own ideas. Manfred Kuehn's book is a fascinating treatment of one of the central figures of western thought.

Harry Gensler is professor of philosophy, John Carroll University, Cleveland, United States.