The Enlightenment was an intellectual movement taking place in the seventeenth and eighteenth centuries. Benjamin Franklin was born in 1706 and died in 1790: therefore his life was spent during the time that is most commonly associated with the Enlightenment. The Enlightenment was mainly defined by the desire to find out what really determined nature, the world, and, therefore, life. The great thinkers of this period demanded more freedom and less restriction. Purely theological reasons were no longer sufficient. Instead, it was reason that philosophers, scientists, and artists tried to use during this period. They strived for knowledge and intellectual freedom.
Franklin had taken great interest in the Enlightenment movement in Europe: he was very much inspired by the thoughts of John Locke, for example. This greatly influenced his own thinking and his view of the world.
Free thinking, morality, and a keen interest in scientific progress were characteristic both of the period of Enlightenment and Franklin himself. For example, in line with the philosophy of the Enlightenment, Franklin did not agree with the authority of Christianity. As a free thinker, he felt limited and restricted by organized faith.
We can also see the spirit of the Enlightenment in his interest in science and his inventions, as he refused to accept the boundaries of current life and instead always strived to learn and discover more. But most importantly, we can see the influence of the Enlightenment movement in his contributions to the American Constitution.