Thomas Jefferson and the Comte de Buffon had fundamentally different understandings of the natural world, a discord that stemmed from Buffon’s “individualism,” that is, what Jefferson saw as a hesitancy to categorically classify species. Such an epistemology, Jefferson argued, threatened to return the scientific community to the days of Aristotle and Pliny. It would undo the order that modern science had worked so diligently to instill in our understanding of the natural world. A belief in the importance of such an order was crucial to Jefferson’s very character. A man of science, he devoted much of his life to discovery, categorization, and systemization.
Different understandings of the natural history of the Americas and of Earth remained central to Jefferson and Buffon’s debate. Jefferson heavily criticized Buffon’s belief that the planet was once hot and has been constantly cooling (which was not an uncommon assertion in the then-nascent field of geology). He also worked to refute Buffon’s incorrect assertion that animals and people in the Americas were smaller than in Europe, known famously as the “degeneracy theory.” This refutation was one of Jefferson’s aims for the Lewis and Clark expedition; he hoped the explorers would find a mammoth that would surpass European species in size.
Despite his disagreements with the Comte de Buffon, Jefferson understood him to be a man of science. In January of 1785, he reminded Francis Hopkinson that Buffon held a position as the head of the British king’s “cabinet of Natural history.” A year earlier, he had described Buffon to Ezra Stiles as a “celebrated Physiologist of the present day.” Despite their academic differences, Jefferson respected Buffon’s position in the intellectual community, never questioning his mental faculties. Ad hominems were not quick to flow from Jefferson’s quill.
While Jefferson frequently challenged Buffon’s scholarship (often skeptical of his renowned mortality rate table), this actually evidences his respect, since he did not always feel the need to intellectually engage with his opponents. In some cases, Jefferson merely brushed them off as the lesser mouthpieces of greater men. For example, in a 1785 letter to the Marquis de Chastellux, he described a man named Robertson as “a compiler only of the relations of others, and a mere translator of the opinions of Monsr. Buffon.” Accordingly, Jefferson’s willingness to engage in what he describes as “conversations with the Count de Buffon on the subjects of Natural history” suggests that the two had, if nothing more, a working relationship.
This relationship was not static, however. In the last years of the eighteenth century, Jefferson’s tone toward Buffon became increasingly negative. Writing to Louis of Parma in February of 1799, he lumped the French scientist in with Robertson although he had been careful, fourteen years earlier, to distinguish the two intellectually. In this letter, Jefferson painted Buffon as a mere dreamer, whose naïve conceptions of natural history he could dispel “with a thousand other facts.” No longer were the two men of science locked in a factual debate. Instead, Jefferson came to see himself as grounded in fact and his opponent as a mere hypothesizer with little real understanding of the natural world.