Anyone who is not a positivist before 25 has no brain; anyone who is still a positivist after age 40 has no heart.
[Positivists promote] the tyranny of the lonely genius, seeking by contemplation in his warm room a universal system to impose upon us all.
An interesting question left largely unanswered in the essay is why introspection and hypothesis testing are so attractive to the young, yet not to the old. Is it because young people are at a comparative disadvantage in exercises that require broad knowledge and understanding? Do they have a comparative advantage in technical statistical work?