Review of Keith Thomson’s "Jefferson’s Shadow: The Story of His Science"

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M. Andrew Holowchak is an Assistant Professor of Philosophy at Rider University.

While books on Jefferson’s intimate life are superabundant, books on Jefferson’s views of science are infrequent. Thus, when I purchased Keith Thomson’s Jefferson’s Shadow, I placed the book beneath a small pile of books “to be read shortly”—a sort of desert in which I was to indulge after having gotten through a main course of more laborious readings on political theory and ethics.

I was surprised to find no motivation for the book by Thomson other than an invitation by Andrew O’Shaughnessy of the International Center for Jefferson Studies. One, for instance, wishes to know how his work differs from other works—specifically, Edward Martin’s excellent Thomas Jefferson: Scientist, or Silvio Bedini’s compendious and more recent Jefferson and Science. What does Thomson add that others have missed? What has Thomson corrected that others have gotten wrong? We are never told.

The book comprises 19 (generally short) chapters belonging to six parts: The Young Jefferson; Natural Science; They, the People; Useful Knowledge; The National Stage; and Philosophical Issues. Par one, The Young Jefferson, might indicate that Thomson is pursuing a historical approach to Jefferson and science. The book does have a loose historical cohesion, but many chapters are broached topically—e.g., chapter 14 begins with Jefferson’s interest in climate in 1776—so there is some confusion apropos of Thomson’s approach.

That noted, the book overall is comprehensive, often reasonable, and even peppered with insights. Thomson’s account of Jefferson’s view of Blacks and American Indians in Part 3 is fair. His treatment of skin color in chapter 11 is especially illuminating. Furthermore, Thomson’s account of Jefferson’s view of the West distinctly captures Jefferson’s optimism, and excitement. Moreover, when Thomson turns to Jefferson’s concern with controlling the pestiferous Hessian fly in chapter 15, he limns some of the political implications of governmental intervention in such issues for Jefferson’s vision of a thriving republic.

Thomson’s writing is relaxed and accessible, but ideas in chapters and paragraphs are often thrown together without regard for relevance. Consider the gallimaufry of ideas in this particular paragraph.

For Jefferson, rhetoric and logic were a crucial complement to Bacon’s teaching on the scientific method itself. He also followed closely Newton’s rules for reasoning. The first was ‘We are to admit no more causes of natural things than such as are both true and sufficient to explain their appearances,’ and the second was ‘Therefore to the same natural effects we must, as far as possible, assign the same causes.’ But Jefferson was not just a philosopher-scientist; he also had a lawyer’s frame of mind (32).


The introductory sentence is about Bacon. Thomson then turns to Newton. He ends with a thought completely out of the blue. How precisely do the three sets of ideas relate to each other?

The book is also riddled with misleading sentiments, if not inaccuracies, that mar the scholarship.

In chapter 3, Thomson sums thus Newton’s first law: “Any object will naturally move in a straight line at a constant velocity” (26). The law of inertia tells us more: that a body in rest in empty space will remain at rest.

In chapters 6 and 7, Thomson writes: “Jefferson believed that the earth had been created by God as described in the Book of Genesis” (73); “He always denied, on grounds of biblical authority, that extinction of species ever occurred”; and “Jefferson … believed in a God who was the creator of all. And thus he gave credence to the account of Creation in Genesis and its implication that the earth was very young and that life on earth had been created only once” (75-6). Jefferson never explicitly makes purchase of the creation account(s) in Genesis. There is no reason to think he took very serious the Old Testament. In his “Syllabus,” Jefferson speaks of the Jewish ideas of deity as “degrading & injurious,” and suggests that the sole contribution of Jewish moral thinking was monotheism.i Thomson unfortunately leads us to none of Jefferson’s writings that might support his view.

In chapter 6, there is Jefferson’s refusal to accept extinction of species. That point is iterated in chapter 8. “He did not believe in extinction, and that view seems to have been based in large part on religious rather than scientific grounds” (89). “Jefferson never changed his mind about extinction of species, although he understood that races and populations … might become extinct” (90). Jefferson’s letter to John Adams (11 Apr. 1823), where Jefferson acknowledges “certain races of animals are become extinct,” Thomson cites as evidence of Jefferson’s refusal to accept extinction. He focuses on Jefferson’s employment of “races,” where he could have used “species.” The letter, ambiguous, could also be taken as grudging acceptance of extinction, for there is no reason to think Jefferson’s use of “races” is not equivalent to “species.” In addition, it seems strange that Jefferson would be close-minded to extinction of species in later life, when so many of the leading scientists of his day had begun to accept it as factual.

In chapter 8, Thomson criticizes Jefferson’s approach to science vis-à-vis his account of the fossilized remains of Megalonyx. Jefferson saw the remains to be those of a great lion of some sort and prepared a paper to be read before the American Philosophical Society in 1797 and published in its Transactions in 1799. When apprized of a similar skeleton of an animal from South America (Megatherium) that was recognized to be a ground sloth, Jefferson did not change his mind, but merely added an appendix to his paper. Thomson says: “Jefferson’s use of the scientific method can be criticized because instead of gathering facts impartially and then analyzing them (the way his idol Bacon had urged), Jefferson had worked a priori. He had started with his lion idea and then tried to prove it. Worse, when that identification was disproven, he still did not completely relinquish the theory” (89).

Even Bacon recognized that one cannot merely gather facts impartially without some at least tentative hypothesis. If one wishes to know why dozens of passengers on a cruise ship have become ill, grouping together the ill and non-ill and seeing what foods each person in both groups has eaten involves the hypothesis,  The cause of illnesses is a type of food. Moreover, Jefferson refused to “completely relinquish” his hypothesis not because his initial “identification was disproven,” but because gaps in the skeletal remains of the two animals led to lingering doubts. Consider Edward Martin’s more circumspect handling of the event over 50 years ago in his book. “This decision [to retain the great-lion hypothesis] was consistent with Jefferson’s own demand that scientific conclusions be reached with greatest caution after the most careful investigation of all the facts. Perhaps he considered his postscript sufficient notice that the identification was tentative.”ii

The final part, “Philosophical Issues,” seems forced—de trop. For illustration, in chapter 17, we are told that Jefferson qua scientist can be placed in context by better understanding Adams’s views of science. Why? We are then told of Adams’s impatience with theory, of his interest in the “generation of Shell fish,” and of other minutiae. Thomson sums, “Digressions and odd enthusiasms notwithstanding, in the realm of science and philosophy, Adams tended to remain the practical man and Jefferson the intellectual” (238). The summation is strained. Jefferson too was fixated on useful knowledge and had little tolerance for knowledge per se. The difference was that Jefferson recognized, as did Hutcheson before him,iii that what at one time seems useless may at another time acquire a use.

In sum, the excitement that I had for the book when I began it quickly diminished. Most of the material in Thomson’s book had been covered and perhaps covered better by Martin. Much of what was not—e.g., all of Part 6—seemed irrelevant. It is unfortunate that Thomson has been unable to improve upon Martin’s book, written 61 years ago.

i Thomas Jefferson, Writings, ed. Merrill D. Peterson (New York: Library of America, 1984), 1124-5.

ii Edward T. Martin, Thomas Jefferson: Scientist (New York: Henry Schuman, Inc., 1952), 109.

iii Francis Hutcheson, A Short Introduction to Moral Philosophy in Three Books; Containing the Elements of Ethicks and the Law of Nature, Second Edition (Glasgow: Robert and Andrew Foulis, 1753), 70-87.


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