O'Shaughnessy doesn't advocate backtesting

[Mark Johnson <janitor@xxxxxxxxxxxx>]

His book "What Works on Wall Street" advocates
a REPETITIVE, MECHANICAL, HUMAN-JUDGEMENT-FREE
approach.  This is what beats the intuitive-judgemental
loosey goosey seat of the pants method.

Mechanical beats intuitive.  That's the thrust of his book.
Backtesting is a minor detail, a teeny piece of the
machinery tucked away under the hood.