A Christian minister from Georgia by the name of Dr. Nelson L. Price wrote on his website, “One of the laws of logic is that you can’t prove a negative.” It’s no surprise that an ignorant religious man would use the “You can’t prove a negative” claim to undermine the justification for atheism, but this is the sort of claim that isn’t unique to such people. The 2008-06-25 Doonesbury comic claimed it was “philosophically impossible” to prove a negative. To make matters worse, I have, ironically enough, seen even *atheists* claim that you can’t prove a negative! So for Christians who wish to undermine atheism, comic strip writers, misguided atheists, and for those who just like reason and logic, let’s discuss this topic.

First, when you encounter someone who says, “You can’t prove a negative,” ask them to prove it. A few seconds after they start trying to prove it, inform them that by proving it they would be undermining their own position that “You can’t prove a negative.”

Second, there are some pretty obvious counterexamples to “You can’t prove a negative” in math, logic, science, and everyday life. One example is Euclid’s proof that there is no greatest prime number. Another example is “There is no married bachelor.” Just delineate the meaning of the term “bachelor” and the rest is fairly self-explanatory. Yet another example (for most people) is “There is no pink elephant before my eyes right now that is highly visible to me.” All one has to do is look and there will be sufficient evidence for the nonexistence of the highly visible pink elephant. So one can prove a negative, both in the sense of rigorous proof like we have in math and logic, and also in the weaker sense of “having sufficiently strong evidence” (as in the case of the highly visible pink elephant). It’s also worth noting that science relies on evidentially-supported negatives all the time; that’s why science has physical laws, which tell us what is and isn’t physically possible.

Atheists above all people should reject the idea that we can’t prove the nonexistence of a thing. Even if “married bachelors” and “the greatest prime number” weren’t obvious examples of things we can prove don’t exist, what about God? Surely we can prove the nonexistence of God, at least in the sense of having sufficiently strong evidence against God’s existence, thanks at least in part to the argument from evil.

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