It’s often argued that you can’t prove a negative – usually in response to someone suggesting that the non-believer needs to prove God doesn’t exist. However, as oft-spouted as it is, it is actually not entirely true; sometimes you can prove a negative.
For example, I can, sadly, prove to you that there is no money in my wallet. The issue arises when the domain (or the ‘Universe of Discourse’ in fancy terms) is too big for our scope or lies outside our access. In regards to the claim that there is no money in my wallet, the domain is quite small and easily within my scope. John Wilkins gives another example, on a somewhat larger scale:
Consider the extinction of the Yellow River dolphin. Pretty well all areas in which that animal can exist are under constant observation by a very large population that has the means to report its existence. So we can safely say that it no longer exists.
If we broaden the domain, and take the statement “there are no aliens in outer space” we will realise that it is too large for our scope – there are parts of space we simply have not yet observed.How much more so then if the domain is outside the universe!
Put simply then, as Wilkins does:
If the domain or universe is small enough, and all the objects in it accessible in a reasonable time, we certainly do think that we can make proof claims.