Responding to the charge of Argumentum ad Ignorantiam

A few months ago an interlocutor put this question to me:

“Did you actually argue that God does not exist on grounds that there is no evidence for the existence of God? I wouldn’t have insulted your intelligence by explaining the argument from ignorance, but I was given to believe that you actually did it.”

Was my intelligence insulted? Maybe, but I hastened to respond.

I’m not sure what exactly was said to you, but “you were given to believe” wrongly if you “were given to believe” that I proclaimed logical proof God’s non-existence based on a lack of evidence for his existence. Whoever “gave to you believe” that I proceed on such a simplistic basis does not know of what he speaks. What I do hold is that proposition that ‘God is real’ is at best a statement of ungrounded faith, given that there are no neutral, objective grounds that support that proposition. The proposition at issue lacks credible credentials. On logical, evidentiary grounds we have as little reason for accepting it as true as we do for accepting the claim that Martians control the world financial markets.

The fallacy of arguing from ignorance does not apply in all cases in which we point to ignorance or a lack of evidence as basis for a conclusion. It does not follow that one argues fallaciously from ignorance whenever one argues that ‘P’ is not likely because there is no evidence adduced for ‘P’. (Suppose that ‘P’ represents the claim that Muslims secretly plan to overthrow the U.S. government.) Sometimes our best information is that there is no evidence to support the claim that P, and when we point this out we are not committing the fallacy of “argument from ignorance.

When I take out my school boy logic text (Irving M. Copi, Introduction To Logic, 6th edition), I read the following:

Argument from ignorance: ..illustrated by the statement that there must be ghosts because no one has ever been able to prove that there aren’t any Generally, the fallacy occurs when it is argued that a proposition is true because nobody has ever proven it false; or when one argues that a proposition is false because nobody has ever proven it to be true. An example of the latter: It is false that there are ghosts because nobody has ever proven that there are ghosts.

The idea being that ghosts might exist although we have not demonstrated that there are such entities. Our ignorance of any proof demonstrating the existence of ghosts is not proof that such things do not exist. To argue otherwise is to base a conclusion on our ignorance. Another example may apply the issue of God’s existence when one argues that God does not exist because nobody has demonstrated (logically from factual premises) that he does exist. To say that our ignorance of any proof of his existence shows that the does not exist would be to commit the fallacy of argument from ignorance.

However, Copi goes on to note that

….in some circumstances it can be correctly assumed that if a certain event had occurred, evidence of it could be discovered by qualified investigators. In such circumstances it is perfectly reasonable to take the absence of proof of its occurrence as positive proof of its non-occurrence. .. the proof here is not based on ignorance but on our knowledge that if the event had occurred it would be known.

This qualification expresses the idea by which I argue that the thesis affirming the existence of a supernatural-God is weakened by a complete lack of evidence to support the thesis. I do not argue that this lack of evidence proves the non-existence of a supernatural-God. Nor do I argue from my ignorance of any proof of God’s existence to conclude that God does not exist. I simply make the reasonable assumption that, if such an entity were real, there would be some neutral, objective evidence to indicate that reality. Given the lack of any such evidence, it is an obviously rational position to hold that most probably such an entity does not exist. The conclusion is not base on ignorance; it is based on knowledge of how the world works and how rational humans proceed.