But you can prove a negative!

There is no way to dis­prove God. There is also no way to dis­prove uni­corns, lep­rechauns, the Loch ness mon­ster or Odin. The inabil­ity to dis­prove does not prove existence.

I hear a lot of peo­ple say this and it sur­prises me, to be very hon­est. This sort of argu­ment is an enthymeme, that enthymeme being “we can’t prove a neg­a­tive”; we can’t prove that God does not exist, or that lep­rechauns, the Lock-ness mon­ster or Odin do not exist. This is “sim­ply” com­pletely wrong. One of the core laws of logic — the law of non-contradiction (a propo­si­tion can­not be both true and not true) — is itself a neg­a­tive. The rule of dou­ble nega­tion also allows us to state any claim as a neg­a­tive (Propo­si­tion P is equal to not-not P).  For instance you can prove you exist, just as you can’t prove you aren’t nonex­is­tent. In other words, if you prove that some­thing is true it fol­lows that you’ve proven it is not not true.

I could prove right now — using a fairly sim­ple induc­tive argu­ment — that uni­corns don’t exist:

1. If uni­corns existed we would have evi­dence in the fos­sil record
2. There is no evi­dence of uni­corns in the fos­sil record
3. There­fore, uni­corns never existed ([1] and [2])

I sus­pect the ‘mod­ern post­mod­ernist’ (ha!) would object to this claim with another enthymeme: “We don’t have a com­plete fos­sil record, you can’t know that”. The enthymeme in this case is that we can’t know any­thing with­out omni­scient knowl­edge of a thing (I sus­pect this is self-refuting, as I’m sure the post­mod­ernist does not have the omni­scient knowl­edge required to make this claim). Which is in itself a mean­ing­less objec­tion, had we a com­plete fos­sil record one could sim­ply reply, ‘Well, no uni­corns fos­silized!’ and the argu­ment is again, undermined.

Rather, that’s not the point of induc­tive argu­ments. An induc­tive argu­ment makes con­clu­sions prob­a­ble, not cer­tain. This would be known as ‘infer­ence to the best expla­na­tion’; “based on all avail­able evi­dence it is prob­a­ble that…” We’re not deal­ing with math­e­mat­i­cal cer­tainty, we can have no such thing in the actual world. So whether we ‘prove God exists’ or ‘prove that God does not exist’ we are deal­ing with the best prob­a­ble expla­na­tion of the evi­dence we have at our dis­clo­sure. In any case, isn’t the claim ‘you can­not prove a neg­a­tive’ itself a negative?

Related posts:

1. And you thought Anselm was absurd?