William Hasker has interesting things to say about the consequences of the standard view that God cannot permit a single instance of gratuitous evil. I won’t fuss the metaphysical issue of the nature of gratuitous evil, but it’s really worth thinking hard about it. I’m interested in Hasker’s claim about what he calls the ‘limited harm principle’, (LH). Here’s the essential argument (EA) for permitting gratuitous evils.
. . . if (LH) is true, and an agent knows it is true, then the agent’s inclination to take moral requirements seriously is likely to be very significantly lessened. But this result is contrary to God’s intention that human beings should place a high priority on fulfilling moral obligations, and should assume major responsibility for the welfare of their fellow human beings. Put more briefly: If we know that God will permit a morally wrong action only if it results in a compensating good, then our motivation to take morality seriously as a guide to life is likely to be seriously impaired.(‘Defining Gratuitous Evil’, Religious Studies, 2010)