Dear Sir, -- Your favor of the 6th instant is just received, and I shall with equal willingness and truth, state the degree of agency you had, respecting the copy of M. de Becourt's book, which came to my hands. That gentleman informed me, by letter, that he was about to publish a volume in French, "Sur la Création du Monde, un Systême d'Organisation Primitive," which, its title promised to be, either a geological or astronomical work. I subscribed; and, when published, he sent me a copy; and as you were my correspondent in the book line in Philadelphia, I took the liberty of desiring him to call on you for the price, which, he afterwards informed me, you were so kind as to pay him for me, being, I believe, two dollars. But the sole copy which came to me was from himself directly, and, as far as I know, was never seen by you.

I am really mortified to be told that, in the United States of America, a fact like this can become a subject of inquiry, and of criminal inquiry too, as an offence against religion; that a question about the sale of a book can be carried before the civil magistrate. Is this then our freedom of religion? and are we to have a censor whose imprimatur shall say what books may be sold, and what we may buy? And who is thus to dogmatize religious opinions for our citizens? Whose foot is to be the measure to which ours are all to be cut or stretched? Is a priest to be our inquisitor, or shall a layman, simple as ourselves, set up his reason as the rule for what we are to read, and what we must believe? It is an insult to our citizens to question whether they are rational beings or not, and blasphemy against religion to suppose it cannot stand the test of truth and reason. If M. de Becourt's book be false in its facts, disprove them; if false in its reasoning, refute it. But, for God's sake, let us freely hear both sides, if we choose. I know little of its contents, having barely glanced over here and there a passage, and over the table of contents. From this, the Newtonian philosophy seemed the chief object of attack, the issue of which might be trusted to the strength of the two combatants; Newton certainly not needing the auxiliary arm of the government, and still less the holy author of our religion, as to what in it concerns him. I thought the work would be very innocent, and one which might be confided to the reason of any man; not likely to be much read if let alone, but, if persecuted, it will be generally read. Every man in the United States will think it a duty to buy a copy, in vindication of his right to buy, and to read what he pleases. I have been just reading the new constitution of Spain. One of its fundamental basis is expressed in these words: "The Roman Catholic religion, the only true one, is, and always shall be, that of the Spanish nation. The government protects it by wise and just laws, and prohibits the exercise of any other whatever." Now I wish this presented to those who question what you may sell, or we may buy, with a request to strike out the words, "Roman Catholic," and to insert the denomination of their own religion. This would ascertain the code of dogmas which each wishes should domineer over the opinions of all others and be taken, like the Spanish religion, under the "protection of wise and just laws." It would shew to what they wish to reduce the liberty for which one generation has sacrificed life and happiness. It would present our boasted freedom of religion as a thing of theory only, and not of practice, as what would be a poor exchange for the theoretic thraldom, but practical freedom of Europe. But it is impossible that the laws of Pennsylvania, which set us the first example of the wholesome and happy effects of religious freedom, can permit the inquisitorial functions to be proposed to their courts. Under them you are surely safe.

At the date of yours of the 6th, you had not received mine of the 3d inst., asking a copy of an edition of Newton's Principia, which I had seen advertised. When the cost of that shall be known, it shall be added to the balance of $4.93, and incorporated with a larger remittance I have to make to Philadelphia. Accept the assurance of my great esteem and respect.