Prominent atheist John W. Loftus gives us an example of a common atheist argument from the size of the universe when he writes:
I think it’s [i.e., the vast size of the universe] even more damaging when it comes to an omnipotent God who supposedly created the universe for the specific purpose of gaining the affections of people on this lone planet of ours. If this is what he desired (for some irrational egotistical reason) he could have simply created us on a flat disk in a much smaller universe like the one the ancients believed existed.
This argument is a hot mess, a mishmash of factual errors,* self-serving assumptions and faulty logic. But let us set most of that aside and focus on Loftus’ argument from personal incredulity.
The argument from personal incredulity takes the form of “I cannot imagine how this could be true; therefore, it must be false.” Notice how Loftus exhibits this fallacy. His argument boils down to the assertion that he cannot imagine why God, if he existed, would have created a large universe. A large universe surely exists. Therefore, God does not exist.
Here is the critical question that is left unanswered: Why should the poverty of John Loftus’ imagination concerning God’s motivations matter to us?
The argument from personal incredulity is a species of the “argument from ignorance.” Duco A. Schreuder writes: “These arguments fail to appreciate that the limits of one’s understanding or certainty do not change what is true. They do not inform upon reality.”
Just so. The limits of Loftus’ understanding about God’s motivations does not change what is true. Indeed, if a God powerful enough to create such a vast universe exists, we can be certain that our understanding of him would be extremely limited. Therefore, it is absurd to suggest that very limited understanding should be the foundation of an argument for his non-existence.
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*His assertion that the ancients had no conception of the scale of the universe, for example, is pure bunkum: “The earth, in relation to the distance of the fixed stars, has no appreciable size and must be treated as a mathematical point.” Ptolemy’s Almagest, Book I, Chapter 6. See also, Psalm 8 (“When I consider thy heavens . . . What is man, that thou art mindful of him?”).