The “dying and rising gods” theory is a currently popular argument against Christianity which states that Jesus was a copycat - or rather that the disciples were simply copying other pagan gods when they claimed that Jesus died and rose again from the dead.
Although this theory has been debunked in the past, it occasionally rears its ugly head requiring a fresh effort to dismantle it. In the following passage taken from his book, Did Jesus Exist?, atheist Bart Ehrman provides just such a demolition of this copycat nonsense. Ehrman writes:
“[Consider] the instance of Osiris, commonly cited by mythicist as a pagan parallel to Jesus. Osiris was an Egyptian god about who a good deal was written in the ancient world. We have texts discussion Osiris that span a thousand years. None was as influential or as well known as the account of the famous philosopher and religion scholar of the second Christian century, Plutarch, in his work Isis and Osiris. According to the myths, Osiris was murdered and his body was dismembered and scattered. But his wife, Isis, went on a search to recover and reassemble them, leading to Osiris’ rejuvenation. The key point to stress, however, is that Osiris does not—decidedly does not—return to life. Instead he becomes the powerful ruler of the underworld. And so for Osiris there is not rising from the dead.
“[Jonathan Z.] Smith maintains that the entire tradition about Osiris may derive from the processes of mummification in Egypt, where bodies were prepared for ongoing life in the realm of the dead (not as resuscitated corpses here on earth). And so Smith draws the conclusion, ‘In no sense can the dramatic myth of his death and reanimation be harmonized to the pattern of dying and rising gods.’ The same can be said, in Smith’s view, of all the other divine beings often pointed to as pagan forerunners of Jesus. Some die but don’t return; some disappear without dying and do return; but none of them die and return.
“Jonathan Z. Smith’s well-documented views have made a large impact on scholarship. A second article, by Mark S. Smith, has been equally informative. Mark Smith is a scholar of the ancient Near East gods and Hebrew Bible who also opposes any notion of dying and rising gods in the ancient world. Mark Smith makes the compelling argument that when [Sir James George] Frazer devised his theory about dying and rising gods, he was heavily influenced by his understanding of Christianity and Christian claims about Christ. But when one looks at the actual data about the pagan deities, without the lenses provided by later Christian views, there is nothing to make one consider them as gods who die and rise again. Smith shows why such views are deeply problematic for Osiris, Dumuzi, Melqart, Heracles, Adonis and Baal.
“According to Smith, the methodological problem that afflicted Frazer was that he took data about various divine beings, spanning more than a millennium, from a wide range of cultures, and smashed the data all together into a synthesis that never existed. This would be like taking views of Jesus from a French monk of the twelfth century, a Calvinist of the seventeenth century, a Mormon of the late nineteenth century, and a Pentecostal preacher of today, combining them all together into one overall picture and saying, “That’s who Jesus was understood to be.” We would never do that with Jesus. Why should we do it with Osiris, Heracles, or Baal? Moreover, Smith emphasizes, a good deal of our information about these other gods comes from sources that date from a period after the rise of Christianity, writers who were themselves influenced by the Christian views of Jesus and ‘who often received their information second-hand.’ In other words, they probably do not tell us what pagans themselves, before Christianity, were saying about the gods they worshipped.
“The majority of scholars agree with the views of Smith and Smith: there is not unambiguous evidence that any pagans prior to Christianity believed in dying and rising gods, let alone that it was a widespread view held by lots of pagans in lots of times and places.” (Bart Ehrman, Did Jesus Exist?, 228-230.)