|A term "achristism" (Henry, 1694), or a-Christ-ism, or a-Jesus-ism, refers to denial of the existence of Jesus Christ as a real person; belief that Jesus never existed.|
In 1694, English nonconformist clergyman Philip Henry (1631-1696), in a letter to Thomas Hunt, coined the term "achristism" as follows: 
“What you write of the paralyzing atheism of the town, I am afraid is too true; but what do you think of such a thing as achristism? I am sure Ephesians 2:12 (Ѻ) mentions both. How many are there that own a god, and worship him, that have no regard to Jesus Christ in doing so; as if we could come to him, and have to do with him, and receive from him, without a mediator! How is he then 'the way?' Hath he not said, 'No man cometh unto the father but by me?' Is he the way to those that do not walk in him, or an advocate to those that do not employ him?”
In 1817, Napoleon Bonaparte, in dialogue with Gaspard Gourgaud, stated things thusly: 
“I have dictated thirty pages on the world’s three religions; and I have read the Bible. My own mind is made up. I do not think Jesus Christ ever existed.”
In 1828, Robert Taylor, in his Syntagma of the Evidences of the Christian Religion, argued the following: 
“Thou hast in this pamphlet all the sufficient evidence, that can be adduced for any piece of history a thousand years old, or to prove an error of a thousand years standing, that such a person as Jesus Christ never existed; but that the earliest Christians meant the words to be nothing more than a personification of the principle of reason, of goodness, or that principle, be it what it may, which may most benefit mankind in the passage through life.”
In 2000, Robert Price, in his Deconstructing Jesus, summarized things as follows: 
“Generations of Rationalists and freethinkers have held that Jesus Christ corresponds to no historical character: There never was a Jesus of Nazareth. We might call this categorical denial ‘Jesus atheism’. What I am describing is something different, a ‘Jesus agnosticism’. There may have been a Jesus on earth in the past, but the state of the evidence is so ambiguous that we can never be sure what this figure was like or, indeed, whether there was such a person.”
In 2001, Kenneth Humphreys, being inspired (Ѻ) by: Earl Doherty (The Jesus Puzzle, 1999); Dorothy Murdock (The Christ Conspiracy, 1999); Timothy Freke and Peter Gandy (The Jesus Mysteries, 1999); George Wells (The Jesus Myth / The Jesus Legend, 1999); Arthur Drews (The Christ Myth, 1910); Robert M. Price (Deconstructing Jesus, 2000); Hyam Maccoby (The Mythmaker: Paul & the Invention of Christianity, 1987); Burton Mack (Who Wrote the New Testament?, 1995); and Elaine Pagels (The Gnostic Gospels, 1979), launched: JesusNeverExisted.com, which turned (Ѻ) 2014 book. 
In 2013, some (Ѻ) were distinguishing between hard “a-Jesus-ism” (akin to hard a-theism) and soft “a-Jesus-ism” (akin to soft a-theism).
In 2015, Libb Thims was listing "achristism", in atheism types by denial and belief, as one of the main categories of denial in respect to "strong atheism".
Noted achristists include: Count Volney (1791) (Ѻ)(Ѻ), Napoleon Bonaparte (1817), Thomas Jefferson (1823), Libb Thims (2003), among others. One can become an achristist, via study of religio-mythology, especially religio-mythology transcription and syncretism, and or possibly by logic deduction, e.g. that miracles are impossible, etc.
An achristist, to note, is not to be confused with “antichrist” (Ѻ); conceptualized, in the Bible, as a false messiah, a figure of concentrated evil, who will face Jesus Christ in his prophesized second coming; one example being Friedrich Nietzsche’s 1888 interpretation of the “antichrist” (Ѻ) term, which has its own unique meaning.
The term “achristism”, meaning to deny the existence of Jesus Christ, to note, seems to have been used by some to mean that a person named "Jesus", as a real person, that walked the earth from 0-33AD, existed, but was not divine (e.g. Einstein), or that he was not part of a trinity (e.g. Newton).
The following are related quotes:
“Jesus Christ in the New Testament, has no reference whatever to any event that ever did in reality take place upon this globe; or to any personages that ever in truth existed: and that the whole is an astronomical allegory, or parable, having invariably a primary and sacred allusion to the sun, and his passage through the signs of the zodiac; or a verbal representation of the phenomena of the solar year and seasons.”— Logan Mitchell (1842), Christian Mythology Unveiled
1. (a) Henry, Philip. (1694). “Letter to Thomas Hunt, Esq., of Boreatton, but then in London”, Jul 5.
(b) Williams, J.B. (1853). Memoir of Rev. Philip Henry (achristism, pgs. 187-88). American Tract Society.
2. (a) Bonaparte, Napoleon. (1817). “Comment to Gaspard Gourgaud”, Apr.
(b) Gougaud, Gaspard. (1898). Talks of Napoleon at St. Helena with General Baron Gourgaud: Together with the Journal Kept by Gourgaud on Their Journey from Waterloo to St. Helena (pg. 276). Nabu Press, 2012.
(c) Haught, James A. (1996). 2000 Years of Disbelief: Famous People with the Courage to Doubt (pg. 109). Prometheus.
3. Price, Robert. (2000). Deconstructing Jesus (pg. 17). Publisher.
4. Taylor, Robert. (1828). Syntagma: of the Evidences of the Christian Religion (Preface) (Ѻ). Publisher.
5. (a) Main – JesusNeverExisted.com.
(b) Humphrey, Kenneth. (2005). Jesus Never Existed: an Introduction to Ultimate Heresy. Publisher, 2014.