Argument from Ignorance
An argument from ignorance treats a claim as established because it has not been disproved, or as impossible because it has not been demonstrated. Ask whether the missing evidence would actually be expected if the claim were true.
THE IDEA
Argument from Ignorance
Argumentum ad ignorantiam (also known as appeal to ignorance). Personal incredulity can produce a related error, but is not the same as relying on a lack of contrary evidence.
Description: The assumption of a conclusion or fact based primarily on lack of evidence to the contrary. Usually best described by, “absence of evidence is not evidence of absence.”
The source’s logical-form section is empty. The examples below illustrate the error.
Example #1: God must exist, because no one can prove that God does not exist.
Explanation: There is an infinity of things we cannot prove – the moon being filled with spare ribs is one of them. Now you might expect that any “reasonable” person would know that the moon can’t be filled with spare ribs, but you would be expecting too much. People make wild claims, and get away with them, simply on the fact that the converse cannot otherwise be proven.
Example #2: Scientists have not found a way to create life from all inorganic substances; therefore, life cannot be created from all inorganic substances.
Explanation: The fact that we have not found a way to create life from all inorganic substances is not evidence that there is no way to create life from all inorganic substances.
Exception: A well-designed search that fails to find something can be evidence against its presence when detection would have been likely. The strength of that evidence depends on the search and the claim; it is not automatically a conclusive disproof.
Tip: Look at all your existing major beliefs and see if they are based more on the lack of evidence than evidence. You might be surprised as to how many actually are.
When to use it
Evaluating claims in debates where one side says 'there is no evidence against X, therefore X is true'.
Assessing scientific hypotheses when absence of evidence is mistakenly treated as evidence of absence.
In a courtroom, arguing that a defendant is guilty because they cannot prove their innocence is an argument from ignorance.
When considering conspiracy theories that rely on the inability to disprove them.
FROM THEORY TO EVERYDAY LIFE
In practice
God's Existence
Claiming God must exist because no one can prove God does not exist. This is a classic appeal to ignorance, as the inability to disprove does not constitute proof.
Creating Life from Inorganic Matter
Arguing that because a process has not yet been demonstrated, it is impossible. Failure to demonstrate it does not by itself establish impossibility; the design and reach of the investigation matter.
A MOMENT TO REFLECT
Put it to work.
Think of a belief you hold that is based more on the lack of evidence against it than on positive evidence for it.
When someone says 'you can't prove that's false,' how can you assess whether that's a valid argument or a fallacy?
Examine a recent debate you had: did either side use an argument from ignorance? How could it have been refuted?
CONTINUE THE CONVERSATION
Source texts
- Logically Fallacious - The Ultimate Collection of Over 300 Logical Fallacies