I'm thinking specifically of his dealing with ceremonial purity laws in the Old Testament. Copan is reacting to what one atheist called, "The Bible's ubiquitous wierdness." Copan spends considerable space explaining why he thinks these purity laws were given and what the symbolism was behind these laws.
For example, Copan suggests that "Genesis 1 divides animals into three spheres: animals that walk on the land, animals that swim in the water, animals that fly in the air." He says that "animals that 'transgressed' boundaries or overlapped spheres were to be avoided as unclean." So eels or shellfish are unclean because they don't have scales or fins (80).
But eels and shellfish don't walk on land or fly in the air. Saying that they've "crossed boundaries" simply because they lack scales or fins seems to be a stretch.
Copan points out that according to Old Testament law, a "clean" land animal must be a "cud chewer" and have split hooves (80).
True, but just because a land animal does not chew the cud or have split hooves, does not mean they have "crossed boundaries." They are still land animals. They don't swim in the sea or fly in the air.
Copan writes "swarming and slithering animals in any sphere (eels, snakes, flying insects) were reminiscent of the fall in Genesis 3 and of the cursed slithering serpent" (81).
I might be able to see Copan's point in the case of the slithering animals, but applying it to flying insects seems to be a stretch.
I agree with Copan that the purity laws in the Old Testament were intended to symbolize the importance of holiness or "set-apartness." God's chosen people were to have lifestyles that were markedly set apart from the degrading, immoral, and idolatrous lifestyles of their national neighbors and the all-pervasive nature of the purity laws were intended as tangible, daily illustrations of that fact.
Although many of Copan's explanations are quite good, for example, he did a good job debunking the theory that some animals were said to be unclean for health reasons (79-80), when Copan feels it necessary to explain why some things were declared to be ceremonially clean and other things were not, I think he has weakened his argument by offering explanations that seem to be scholarly conjectures at best. The fact is that the Bible itself doesn't explain why some things are said to be clean and others unclean.
If Copan's point is only that there may be valid reasons behind laws that may seem arbitrary and "weird" to us, I agree, but his argument has been weakened by not making that point explicitly.
I think I would approach the topic from a different angel.What if there is no reason why some things are declared clean and others are declared unclean? If God wanted to set before His people a symbolic but tangible reminder of how important holiness or "set-apartness" was to Him, why should we think that there must be a reason for why some things are "clean" and other things are not?
For example, maybe there was nothing fundamentally holy about a cow or fundamentally immoral about a pig? (From a Christian perspective, this is supported in the New Testament by the fact that unclean foods are declared clean). The point was only to provide a daily, tangible reminder that separateness (holiness) was important to the God of Israel. God could just as well have said, you may eat green things which are "clean" but you must avoid red things (like red peppers or apples) which are unclean. My guess is that if God had said to avoid red apples someone would probably have conjectured that this was because it was reminiscent of the fruit that caused the fall of Adam and Eve!
My point is that the reason for clean and unclean animals did not lie so much in the animal itself, but in the illustration. The reason was to provide a daily tangible reminder of the importance holiness--something about which modern atheists (and many Christians, for that matter) seem to be clueless.
Finally, regarding what one atheist called, "The Bible's ubiquitous weirdness" I would answer that this smacks of ethnocentrism or cultural snobbery. Some condemn the "weirdness" of the Bible because it looks strange to them from the perspective of their own 21st century, Eurocentric culture. Although they may be very tolerant of all other cultures and are often blind to the weirdness of our own culture, they are very selectively intolerant of ancient Jewish culture.
I'm only up to chapter eight but so far the book has been excellent, notwithstanding my nit-picky criticisms.