Thomas Jefferson Papers

To Thomas Jefferson from John Rush, 15 October 1804

on or before 15 Oct. 1804


In presenting you with the Elements of life I have given you merely the Alphabet of this science. Mankind are not yet prepared for the consequences which would flow from principles, deduced from Nature and reason. Physical morality can never perfect human nature, while the physical world and its enjoyments, are abandoned for that of the moral—I have therefore touched lightly on solid ground. But perhaps I have unfolded the true germ, from which has sprung a great portion of error, by unfolding the difference between the truth of ideas and the truth of facts;—a difference, that though known to many Philosopher, has not by them been applied, to establish first principles.

To you Sir my allusions will be familiar; and your mind can much better supply what I have omitted to conclude. I wrote only for men of science, but with this reserve, that if attacked by pretenders, I should explain some things in a manner somewhat subversive of their logical reasonings—I might have shown them, that it requires a stronger effort of the mind, to comprehend the truth of a simple proposition, than it does to understand, the most abstract proposition in metaphysics.

I have been asked, why I did not consider the doctrine of “Epigennesis” or preexisting germs? but I have provided for this,—for if every known form of matter consists in the particular union of Chemical Elements, the germ is nothing else but chemical matter, resulting from affinity; and its vegatation, or expansion, the consequence of other matters agreeably to Affinity—We talk of Embios in the semen masculinum; I have seen them, and lo! they were tadpoles, which upon mixture with the fluid in the female organs, undergoes a total decomposition—At any rate a chemical change is proved to take place, for if every germ were a man in minature, we should have a thousand at a birth—but all these are decomposed and go to form the heart and arteries, which perhaps first appear—These certainly do not appear until the germs have undergone a change.

With Sentiments of high respect I am Sir your Obt

J Rush

DLC: Papers of Thomas Jefferson.

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