Christians believe that the world was made by a Jewish man.
That is the foundation of the Christian religion.
The Gospel of John chapter 1 reveals the naivete of the belief:
10He was in the world, and the world was made by him, and the world knew him not.
11He came unto his own, and his own received him not.
12But as many as received him, to them gave he power to become the sons of God, even to them that believe on his name:
13Which were born, not of blood, nor of the will of the flesh, nor of the will of man, but of God.
14And the Word was made flesh, and dwelt among us, (and we beheld his glory, the glory as of the only begotten of the Father,) full of grace and truth.
15John [the Baptist] bare witness of him, and cried, saying, This was he of whom I spake, He that cometh after me is preferred before me: for he was before me.
16And of his fulness have all we received, and grace for grace.
17For the law was given by Moses, but grace and truth came by Jesus Christ.
The central figure of the cult, Jesus, is based on a real man. If he were purely invented he would have been called Immanuel, meaning “God with us”, as prophesied by Isaiah (7:14). His story as told in the Gospels and the Epistles of the (Greek) “New Testament” is almost entirely fiction, tailored to fit the prophecies of the Jewish religious books.
Very little is known about the living man after whom the cult was named. A few sayings might have come from him, such as: Matthew 10:5-6: “These twelve Jesus sent forth, and commanded them, saying, Go not into the way of the Gentiles, and into any city of the Samaritans enter ye not. But go rather to the lost sheep of the house of Israel.” (King James Version.)
The First Council of Nicaea (325 CE) laid down that Jesus Christ was “both fully human and fully divine”. Two in one.
Pius Christians deny the nonsensical origin of their belief; ignore as much as possible the horrors of actual Christian history such as, and chiefly, the Inquisitions of the Papacy and Spain; blame the Jews for crucifying Jesus - the punishment meted out to all rebels against the Roman Empire - to help the Romans free themselves of the unjust deed.
The Jesus of Christian legend commits offenses against Judaism. He commends the beauty of the lilies who “toil not neither do they spin”, which would have been against the order of God to Adam and Eve and so to all humankind: “In the sweat of thy brow shalt thou eat bread.” More importantly, he launches a revolution of religious belief by substituting love for justice as the core value of his putative religious teaching.
Saul/Paul, held by Christians to be the first and chief spreader of the teaching of Jesus to the gentiles - adding, according to his own letters, doctrines and stories of his own invention (such as the “last supper”) - was almost certainly not a Jew. (If he was a Jew, he had not been raised in the faith.) He was not a clever man, nor a good writer. To ascribe to him, as is done, the beautiful poem of 1 Corinthians 13: “Though I speak with the tongues of men and of angels, and have not charity, I am become as sounding brass, or a tinkling cymbal” - arguably the only beautiful poem in the “New Testament” - is to wildly misjudge the man.
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Why did Christianity spread as it did? See my essay here:
https://theatheistconservative.com/the-birth-and-early-history-of-christianity/