Alexander von Humboldt grew up in a time of radical change in human thought. He witnessed the movement of Enlightenment and significant political transformations first-hand and they had a lasting impact on him. In the following paragraph, biographer Andrea Wulff describes Humboldt's motivation to meet U.S. President Thomas Jefferson on his return from the South American expedition: 

From a young age Humboldt had been surrounded by Enlightenment thinkers who had planted the seeds of his life-long belief in liberty, equality, tolerance and the importance of education. But it had been the French Revolution in 1789, just before his twentieth birthday, that had determined his political views. Unlike the Prussians who were stilled ruled by an absolute monarch, the French had declared all men equal. Since then Humboldt had always carried the 'ideas of 1789 in his heart'. He had visited Paris, in 1790, where he had seen the preparations for the celebration of the first anniversary of the revolution. So enthused had Humboldt been that summer that he had helped to cart sand for the building of a 'temple of liberty' in Paris. Now, fourteen years later, he wanted to meet the people who had forged a republic in America and 'who understood the precious gift of liberty'.

—Andrea Wulf, The Invention of Nature. Alexander von Humboldt's New World. New York, Alfred A. Knopf. 2016.