As a more specific example, consider the size of the human brain. If God exists, then it necessarily follows that a fully functional mind can exist without a body–and if that is true, God would have no reason to give us brains. We would not need them. For being minds like him, being “made in his image,” our souls could do all the work, and control our thoughts and bodies directly. At most a very minimal brain would be needed to provide interaction between the senses, nerves, and soul. A brain no larger than that of a monkey would be sufficient, since a monkey can see, hear, smell, and do pretty much everything we can, and its tiny brain is apparently adequate to the task. And had God done that–had he given us real souls that actually perform all the tasks of consciousness (seeing, feeling, thinking)–that would indeed count as evidence for his existence, and against mere atheism.
In contrast, if a mind can only be produced by a comparably complex machine, then obviously there can be no God, and the human brain would have to be very large–large enough to contain and produce a complex machine like a mind. Lo and behold, the human brain is indeed large–so large that it kills many mothers during labor (without modern medicine, the rate of mortality varies around 10% per child). This huge brain also consumes a large amount of oxygen and other resources, and it is very delicate and easily damaged. Moreover, damage to the brain profoundly harms a human’s ability to perceive and think. So our large brain is a considerable handicap, the cause of needless misery and death and pointless inefficiency–which is not anything a loving engineer would give us, nor anything a good or talented engineer with godlike resources would ever settle on.
Richard Carrier, Why I Am Not A Christian, page 62
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