Husserl , after his Platonic turn , pointed out that the failure of anti-psychologists to defeat psychologism is a result of being unable to distinguish between the theoretical side of logic ( which tells us what is - descriptive ) , and the normative side ( which tells us how we ought to think - prescriptive ) . Husserl pointed out that the failure of anti-psychologists to defeat psychologism was a result of being unable to distinguish between the foundational , theoretical side of logic , and the applied , practical side .