Appeal to Ignorance

Logical fallacy

Treating the absence of proof against a claim as proof of it, or the absence of proof for a claim as proof against it.

An everyday example

“Nobody has shown this supplement doesn't work, so it works.”

The same move in this debate

“Nobody has proved fish are conscious, so they aren't.”

Where this appears

Rests on the possibility that plants might have experiences we cannot detect, and treats that uncertainty as though it established the claim rather than leaving it unsupported.

Fish don't feel painEthics & Morality

The inference runs from 'we cannot directly verify their experience' to 'there is none'. The same inferential barrier exists for other humans, and is not treated as decisive there.

I've never been taught in medical school to recommend a vegan dietHealth & Nutrition

The speaker treats the absence of any instruction to recommend a vegan diet as if it were evidence that the diet is inferior or not recommendable. Never being told to recommend something is not the same as being told not to.

Animals eating their natural diet don't get diabetes, cancer or heart diseaseHealth & Nutrition

The argument reads the absence of recorded chronic disease in wild animals as proof that the disease is absent. Wild animals mostly die young and are rarely examined, so the lack of diagnoses reflects missing data, not good health.

Heart attacks were unheard of before about 1910, so they can't be caused by traditional animal foodsHealth & Nutrition

The claim treats the lack of documented heart attack deaths before 1910 as proof that heart attacks did not happen. But the condition had not yet been clinically described, so no such records could exist whether or not people were dying of it.

Reviews show the studies linking red meat to cancer are poor qualityHealth & Nutrition

The review found the evidence of harm from unprocessed red meat was weak, not that red meat was shown to be harmless. The arguer treats the lack of strong proof of harm as though it settled the question in meat's favour.

We keep discovering new things, so don't cut out a whole food groupHealth & Nutrition

Treats the possibility of undiscovered beneficial compounds as a reason to believe they exist and matter, when not yet knowing something is not evidence either way.