Such facts show us what is the value of the testimony of crowds. Treatises on logic include the unanimity of numerous witnesses in the category of the strongest proofs that can be invoked in support of the exactness of a fact. Yet what we know of the psychology of crowds shows that treatises on logic need on this point to be rewritten. The events with regard to which there exists the most doubt are certainly those which have been observed by the greatest number of persons. To say that a fact has been simultaneously verified by thousands of witnesses is to say, as a rule, that the real fact is very different from the accepted account of it.