A metal drafting compass stands over an unfinished circle on cream paper.

Original artwork, not a still

Mostly Harmless • 1992

Douglas Adams

Now logic is a wonderful thing but it has, as the processes of evolution discovered, certain drawbacks. Anything that thinks logically can be fooled by something else which thinks at least as logically as it does.

Behind the line

What it means

Our interpretation.

The passage praises logic, then argues that reasoning alone offers no protection from deception by an equally capable reasoner. Its appeal to evolution frames this as a limitation of rational thought. The point is that thinking logically does not make a mind impossible to outwit.

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