"Never did We send a messenger or a prophet before you, but, when he framed a desire, Satan threw some (vanity) into his desire: but Allah will cancel anything (vain) that Satan throws in, and Allah will confirm (and establish) His Signs: for Allah is full of Knowledge and Wisdom." (Quran 22:52)
Debate Question: Why does Allah have Satan "throw some vanity into" the desires of the prophets, instead of doing this by himself?
"That He may make the suggestions thrown in by Satan, but a trial for those in whose hearts is a disease and who are hardened of heart: verily the wrong-doers are in a schism far (from the Truth)" (Quran 22:53). Here Allah endeavors to provide a reason for permitting Satan to influence prophets. Debate Question: If Allah saw value in "a trial for diseased hearts" alive back then, why not keep the verses in the Scripture, so that these Satanic verses could yield trials for all those with diseased hearts who will come later?
Even more major Debate Question: What could possibly be the logical reason for Allah to create a devil like Satan in order to misguide people?