Negative evidence
Negative evidence is a significant gap in expected knowledge or evidence for a phenomenon. If a proposed theory would logically produce a certain kind of evidence, then the absence of that evidence, or the negative evidence, is suggestive that the theory is mistaken. If your neighbor claimed that teenagers were racing their cars outside of his house, the absence of teenagers, cars and tire marks on the street would be negative evidence against his claim.
While useful in evaluating theories, negative evidence can be a dangerous tool. It is highly subjective, because it is predicated on our expectations, and it is always uncertain, because new evidence might be obtained to fill the gap.
Taken too far, negative evidence becomes an appeal to ignorance, the mistake of believing that because we have not found evidence, it must not exist. Negative evidence is often used in this capacity by advocates of creationism, who argue that we should have found more fossil evidence of intermediate species if evolution is correct.
“”The absence of evidence is not the evidence of absence.
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