"One reason would be to communicate with us more effectively. Imagine you are watching a farmer plow a field. You notice that an ant hill will be plowed under by the farmer on his next time around. Because you love ants, you run to the ant hill to warn its tiny inhabitants. First you shout to them the impending danger, but they continue their work. You then try many other form of communication, but nothing seems to get through to the imperiled ants. You soon realize that the only way you can really reach them is by becoming one of them."This is one of the worst metaphors for anything that I have ever seen. There are quite many things horribly wrong with it.
- According to Christian theology, including the one that McDowell himself accepts, God created everything. In terms of this metaphor, that means that this person shouting the warnings is the one who created the ant hill, the field, the plough and the farmer. Moreover, this person knew perfectly well in advance what would happen when he created those things. Therefore it's fully and completely God's own fault that this is happening.
- If "God" here wanted to save the ants, the rational thing to do would be, rather obviously, to stop the farmer. This especially so because "God" had created the farmer and the plough in the first place...
- This metaphor is painting God as limited and impotent. It seems to be saying that God cannot stop the farmer and the plowing, that it's completely out of his influence and authority, something that he cannot do anything about. He cannot even do as much as take the ant hill and move it somewhere else. The only thing that God is able to do is go to the ant hill and shout at it. This goes blatantly against the concept of an omnipotent god in Christian theology.
- It likewise paints God as limited because he's completely unable to directly communicate with the ants. This not only goes against Christian theology about God's omnipotence, but it also directly contradicts the Bible, given that it contains numerous instances of God directly communicating with people. The metaphor seems to be saying that God cannot communicate directly with us (for whatever reason), even though that's very clearly not the case in the Bible.
- The man (who should be omnipotent) becoming an ant is most certainly not the most effective way of communication. Direct communication, which the god described in the Bible is perfectly capable of doing, would be a lot more efficient. Him becoming one of the ants and preaching to them the impending disaster is actually one of the least effective ways of getting the message through that one can think of. It's more or less guaranteed that a significant portion of the population will never even hear the message, and even from those who do, a significant portion won't believe it. Direct communication would be a lot more convincing and effective.