When he was thirteen, Einstein spent much time and energy with philosophy, particularly the works of Immanuel Kant. Kant was a philosopher who lived from 1724 to 1804. He was born in Konigsberg, East Prussia, which today is part of Russia.

Unlike Einstein, Kant was raised and schooled with the religious tenets of Pietism, an offshoot of Christianity with heavy evangelical roots. Studying the Bible and attending devotionals were important aspects of this religion. Kant's father was a saddle maker and his mother was unemployed, so Kant was the first in his immediate family to attend university.

Kant spent all of his life cloistered in his small town. He never left the city, let alone the country. He never married, and left his house only to go to his university and take a daily walk. Like most of Einstein's intellectual mentors, Kant was a teacher; he taught a range of courses in both mathematics and logic at the University at Konigsberg.

Key Elements of Kant's Theories

Kant published his first work, Thoughts on the True Estimation of Living Forces, at the age of twenty-two. One of Kant's main theories was that the basic, underlying foundations for mathematics and science could be known “a priori”–by intuition, not experience. Reason was, for Kant, insufficient in establishing the laws upon which the universe rested. A certain amount of trust or faith in human intuition was mandatory. People, then, were at least as important as fact in interpreting the world everyone inhabits. Kant's ideas were consistent with the European Enlightenment, a movement that was going on during Kant's lifetime throughout Europe.

These aspects of Kant's philosophy were shown by another of his most important beliefs. He wrote about how representation made the existence of an object possible; it was not, for Kant, that the object itself made representation possible. For example, an apple wouldn't exist if there were no way to see or describe it. This view differed from that of other philosophers in that Kant's contemporaries might have said that it was the apple itself that made seeing or describing it possible. Kant's basic philosophy focused on the idea that human contribution was essential to understanding.

The Categorical Imperative

Another of Kant's major contributions to philosophy came in the area of ethics. He had a theory known as the categorical imperative, an idea that morality depended on one single command (an imperative is a command). In other words, morality was absolute. This maxim can be interpreted as saying, act as if everything you do comes from and creates a universal truth. Kant's view is opposite to a contemporary notion called the hypothetical imperative, which stated that morality is conditional. “If your foot hurts when you kick the wall, stop kicking the wall” is an example of a hypothetical imperative.

Kant published one of his best-known works, The Critique of Pure Reason, in 1781. In this work he describes the notion of “a priori” knowledge that doesn't come from experience. He also explores how philosophy should use science and math to try and figure out how much knowledge can come from intuition alone, and how much requires experience.

Einstein studied The Critique of Pure Reason extensively. So how might Kant's ideas have influenced Einstein's early thinking? Much of Kant's philosophy is based on its relationship with mathematics and physics, subjects of clear interest to Einstein. However, Kant's theories of intuition implied, to some extent, that much of the world was just an illusion, and not something proven by hard scientific fact. The world only existed, for Kant, because living creatures were there to represent it. Einstein would take issue with much of this aspect of Kant's philosophy.