In the recounting of the story in Genesis 22, God wishes to test Abraham and see whether he "fears God." To this effect, God commands Abraham to go and sacrifice his only son, Isaac. On the third day of their journey Abraham takes Isaac up to a mountain to sacrifice him. Before going up, Abraham tells his servants with him, "We shall worship and come back to you." (Genesis 22:5) Abraham then binds Isaac and prepares to sacrifice him. When Abraham grabs his knife to kill Isaac an angel sent from God stops him by telling him not to kill the boy. God speaks through the angel and says that he now knows that Abraham fears him, and because of his actions God will shower blessings upon Abraham and his descendants.
Sometimes opponents of Christianity will say that this verse proves an inconsistency in the Christian conception of God. On the one hand, God is supposed to be a perfect being, and a perfect being, it seems, would never command something intrinsically evil such as sacrificing an innocent person to him. On the other hand, the Bible says he does. Let's give a precise argument which captures the force of this more vaguely formulated one.
- (1) Suppose God commands Abraham to sacrifice another innocent human being to him. [assumption]
- (2) God commands someone to do an action A only if it is morally licit to do A. [premise]
- (3) So it is morally licit to sacrifice another innocent human being to God. [by 1 and 2]
- (4) But it is not morally licit to sacrifice another innocent human being to God. [premise]
- (5) So God did not command Abraham to sacrifice another innocent human being to him. [by 1 through 4]
But the conclusion of the argument contradicts Christianity, first of all and primarily because it asserts that something which the Christian Scriptures say happened actually didn't happen. But I'd argue that even if one didn't think we had to take the story literally, the story of the sacrifice of Abraham and Isaac is in another sense central to Christian teaching, and the conclusion would still disprove Christianity.
Throughout the New Testament the story is frequently cited with approval as a prefigurement of what God would do with Christ. Moreover, Abraham and the way he acted here is constantly given as a paradigmatic instance of true faith and fear of God. (For verses, see e.g. Acts 3:25; Romans 4:1; Romans 8:32; Hebrews 11:17) So, if one could show that the story couldn't have happened (in both the metaphysical and the deontic sense) then the New Testament is theologically mistaken, both in comparing the central mystery of Christ's sacrifice to Abraham's, and in upholding Abraham as an example of faith.
It's important then for Christians to diffuse the argument above. I want to respond to the charges in a way that is somewhat less common. Some people try to criticize premise (4) and say that actually since God commanded a sacrifice of an innocent human being it was morally licit to do so. Instead, leaving (4) aside, I want to criticize premise (2). Premise (2) seems true though. God, a perfect being, could not command something evil, could he? Despite appearances, I think that premise (2) is false. However, the exceptions to (2) are far and few between. One could even argue that the exceptions are precisely those cases which are like the Abraham and Isaac case.
Suppose that, as (4) says, it is not morally licit to sacrifice another innocent human being. However, suppose Abraham doesn't know this. One might wonder how Abraham could fail to realize this unless he was morally obtuse, and we know that Abraham was a pretty decent guy. However, one might begin to at least doubt one's own moral intuitions if one were appeared to by God in all his glory and commanded to do something one previously thought was wrong. It's quite easy for us to say that (4) is true when we don't have the Almighty before us saying otherwise, but one should at least be somewhat sympathetic if Abraham doubts it, given his circumstances.
So, this gets to why I think (2) is false. Suppose God knows that if he were to tell Abraham to sacrifice Isaac then Abraham would doubt (4). (Note: One need not appeal to Molinism here, since this counterfactual about doubting could be true regardless as to what Abraham would freely do in the situation.) Then, I contend, God could command a morally illicit action to test Abraham's faith, so long as God does not intend for it to actually come about in the end. By doing so, God does not engender any evil volitional attitudes in Abraham, since Abraham could be unsure about the truth of (4), at least when commanded otherwise by God, and Abraham could then take God's omniscience and moral authority as sufficient justification for trusting that whatever he does must be morally OK.
In other words, Abraham could (without fault) begin to doubt the truth of (4), because of his very concrete and vivid experience where the almighty God commanded him to do something contrary to it. Then, since he knows the all-knowing and perfectly good God commanded it, Abraham can (without fault) place his trust in God that he is not doing something wrong and intend to bring it about.
Of course, throughout all this, God knows that if Abraham were to actually bring about the slaughter of his innocent son, then Abraham would have done something which is not morally licit. And so God doesn't actually intend for Abraham to do it. But Abraham doesn't know this. Since Abraham doesn't know this, Abraham is in a state where God can truly test him, not only to see whether Abraham is willing to give up everything he has for him including his only son, but also whether Abraham trusts in God's goodness and moral authority. Since God is doing this only to test Abraham's faith, and does not actually intend to bring about any evil whatsoever, nor does he make Abraham do anything evil, it is not contrary to God's goodness to command an evil action in these circumstances.
So, in sum, (2) is false, because God can command a morally illicit action if (i) God does not intend to actually let it be brought about, (ii) the people he commands do not know that it is morally illicit and (iii) God wants to test their faith and obedience to him in some way. And these conditions are satisfied in the case of Abraham and Isaac.