Final answer:
The hidden premise is that evil is utterly pointless, which is debated in philosophical and theological discourse regarding the problem of evil and its reconciliation with a deity characterized by omniscience, omnipotence, and benevolence.
Step-by-step explanation:
The hidden premise in the statement "if a good and powerful God exists, he would not allow pointless evil" appears to be the assumption that evil is entirely pointless and without any potential for resulting in a greater good or serving some greater purpose.
This premise is often challenged by the argument that what may seem to be pointless evil could, from a divine perspective, serve a larger, ultimately beneficial scheme that is beyond human comprehension.
The philosophical issue at hand is the problem of evil, which raises questions about the compatibility of evil with an omniscient, omnipotent, and perfectly good deity.
Traditional theologians and philosophers have proposed various responses to this dilemma, including the perspectives that evil is a necessary counterpart to free will,
that evil is not an actual substance but rather the absence of good (privation theory), or that existing evil may be part of the 'best possible world' with the greatest balance of good over evil overall.