Many theists are fond of linking the problem of evil with a moral argument for God’s existence. The idea is that by making an argument from evil against God’s existence, the atheist has supposedly contradicted herself since the the argument from evil presupposes an objective evil and objective evil, in turn, presupposes God’s existence.
Since I’ve refuted that claim before, I want to explore a different aspect of linking these two kinds of arguments, namely, the double standard which some theists apply to these (allegedly) linked arguments. When it comes to the problem of evil, these theists will say there are two kinds of arguments from evil, logical and evidential. Logical versions claim that God and evil are logically incompatible, while evidential versions merely claim that evil is evidence against God. These theists will be quick to tell you that logical arguments from evil were discredited long ago by Alvin Plantinga, who demonstrated there is no logical inconsistency between:
(1) God exists.
(2) Evil exists.
Yet these same theists seem to forget everything Plantinga taught them about proving two propositions are logically inconsistent when it comes to making a moral argument for God’s existence. Since these theists think the problem of evil is linked to (their favorite version of) the moral argument for God’s existence, it’s hypocritical for them not to apply the same logical scrutiny to both families of arguments.
Allow me to expain. Let’s begin by saying there are two kinds of moral arguments for God’s existence, logical and evidential. Logical versions claim that moral values and/or duties are logically incompatible with God’s nonexistence, while evidential versions merely claim that moral values and/or duties is evidence for God’s existence. Using the exact same techniques applied by Plantinga to logical arguments from evil, these theists should recognize that no one has ever successfully proven a logical contradiction between atheism and objective morality. To be precise, no one has ever proven that:
(3) God does not exist.
(4) Objective moral values and/or duties exist.
are logically inconsistent.
It seems rather one-sided and, indeed, hypocritical to require proof of logical inconsistency when it’s convenient (in response to an atheistic argument) but then not require the parallel proof when it’s inconvenient (in support of a theistic argument).
For my part, I agree that Plantinga refuted J.L. Mackie’s logical argument from evil and I think no one has ever demonstrated a logical incompatibility between atheism and ontologically objective moral values or duties.