As for Jefferson, I get the impression he might have been a closet atheist.

Afraid not, but if it gives you comfort to believe it . . .

But enough of criticism: let me turn to your puzzling letter of May 12. on matter, spirit, motion etc. It's croud of scepticisms kept me from sleep. I read it, and laid it down: read it, and laid it down, again and again: and to give rest to my mind, I was obliged to recur ultimately to my habitual anodyne, ‘I feel: therefore I exist.’ I feel bodies which are not myself: there are other existencies then. I call them matter. I feel them changing place. This gives me motion. Where there is an absence of matter, I call it void, or nothing, or immaterial space. On the basis of sensation, of matter and motion, we may erect the fabric of all the certainties we can have or need. I can concieve thought to be an action of a particular organisation of matter, formed for that purpose by it's creator, as well as that attraction in an action of matter, or magnetism of loadstone. When he who denies to the Creator the power of endowing matter with the mode of action called thinking shall shew how he could endow the Sun with the mode of action called attraction, which reins the planets in the tract of their orbits, or how an absence of matter can have a will, and, by that will, put matter into motion, then the materialist may be lawfully required to explain the process by which matter exercises the faculty of thinking. When once we quit the basis of sensation, all is in the wind. To talk of immaterial existences is to talk of nothings. To say that the human soul, angels, god, are immaterial, is to say they are nothings, or that there is no god, no angels, no soul. I cannot reason otherwise: but I believe I am supported in my creed of materialism by Locke, Tracy, and Stewart.

At what age of the Christian church this heresy of immaterialism, this masked atheism, crept in, I do not know. But a heresy it certainly is. Jesus taught nothing of it. He told us indeed that `God is a spirit,' but he has not defined what a spirit is, nor said that it is not matter. And the antient fathers generally, if not universally, held it to be matter: light and thin indeed, an etherial gas; but still matter. Origen says `Deus reapse corporalis est; sed graviorum tantum corporum ratione, incorporeus.' Tertullian `quid enim deus nisi corpus?' and again `quis negabit deumesse corpus? Etsi deus spiritus, spiritus etiam corpus est, sui generis, in sua effigie.' St. Justin Martyr `{to Theion phamen einai asomaton oyk oti asomaton—epeide de to me krateisthai ypo tinos, toy krateisthai timioteron esti, dia toyto kaloymen ayton asomaton.}' And St. Macarius, speaking of angels says `quamvis enim subtilia sint, tamen in substantia, forma et figura, secundum tenuitatem naturae eorum, corpora sunt tenuia.' And St. Austin, St. Basil, Lactantius, Tatian, Athenagoras and others, with whose writings I pretend not a familiarity, are said by those who are, to deliver the same doctrine. Turn to your Ocellus d'Argens 97. 105. and to his Timaeus 17. for these quotations. In England these Immaterialists might have been burnt until the 29. Car. 2. when the writ de haeretico comburendo was abolished: and here until the revolution, that statute not having extended to us. All heresies being now done away with us, these schismatists are merely atheists, differing from the material Atheist only in their belief that `nothing made something,' and from the material deist who believes that matter alone can operate on matter.

Rejecting all organs of information therefore but my senses, I rid myself of the Pyrrhonisms with which an indulgence in speculations hyperphysical and antiphysical so uselessly occupy and disquiet the mind. A single sense may indeed be sometimes decieved, but rarely: and never all our senses together, with their faculty of reasoning. They evidence realities; and there are enough of these for all the purposes of life, without plunging into the fathomless abyss of dreams and phantasms. I am satisfied, and sufficiently occupied with the things which are, without tormenting or troubling myself about those which may indeed be, but of which I have no evidence. I am sure that I really know many, many, things, and none more surely than that I love you with all my heart, and pray for the continuance of your life until you shall be tired of it yourself.