Now then, I tell you the truth: Three more kings will arise in Persia, and then a fourth, who will be far richer than all the others. When he has gained power by his wealth, he will stir up everyone against the kingdom of Greece.
Historically speaking, we know that more than four kings have ruled over Persia, yet the text in Daniel asserts that only four kings ruled over Persia before it succumbed to the mighty Macedonian/Greek empire. Why is that?
We do know that the schema of four successive kings/kingdoms has been a common motif in the Persian literature, and that the author of Daniel most probably drew from these sources as is evident from the dream of the four beasts in chapter 2. So could it be that the number four here is used rather liberally by the author through poetic license but is not meant to be taken literal, or is there some justification for the number four in relation to the Persian empire (perhaps it refers to four great kings of Persia) or is there any other deeper intended meaning (spiritual, symbolic) here that I'm missing?
Regardless of the question whether this prophecy was written before (and is thus genuine) or after the events, this passage seems problematic, since it doesn't seem to reflect the historical reality in the Persian empire.