His opening sentence highlights ridiculous French laws, regarding diet and medicine, denying individuals the right to look after their body as they deemed fit. Once into the realms of science, philosophy and experimentation, his comments on Galileo, by how he phrases them, show his great admiration for the man and his work. His brilliant use of irony indicting the government in question, suggests it was legislating against the mind. New ideas and discoveries should be encouraged rather than punished. Jefferson ridicules that government in Galileo's case for its reaction against reason and innovative thinking. His tongue-in-cheek phrase:
The quotation reflects their philosophies. Bacon took Galileo's work and formalized it, suggesting that challenging orthodoxy, observing nature, using reason, would lead to true knowledge - experimentation would verify it. Jefferson incorporates Bacon's philosophies and methods, now
He rejects some of the Rationalism of Descartes; that excluding reference to the external world, suggesting knowledge is gained by reason alone. Jefferson, a man of science and practical action, accepted the ideas of critical questioning, but was less impressed with the concept of thought without investigation or experimentation. The inference here may be that this particular founding-father of the Enlightenment did not wholly fit with Jefferson's views.
The quotation provides evidence of his admiration and commitment to the work and philosophy of Isaac Newton, containing reference to his theory of gravity, and how its power and truth was accepted through reason, not legislation. Newton is a seeker after the truth whose findings could not be overturned. Newton took Galileo's work and and astrological studies of his time, defined natural laws, and presented incontrovertible truths. Scientific research, experimentation, sharing the knowledge, were all aspects of the man whose thinking Jefferson admired. His remarks regarding Newton prove he is reflecting Enlightenment thinking and values.
There is a connection between Jefferson's own religious beliefs and the upsurge of Natural Theology which resulted from Newton's work. The idea that Nature is proof of the Divine, a Master Designer, appealed to Jefferson, who espoused the aspect of Scientific Deism, which contends that Nature was the result of Divine Creation, then goes on to operate under universal laws. Jefferson sees in Newton what Enlightenment means in practice.