I am having a difficult time understanding the critique of psychologism. From Dan Zahavi's book Husserl's Phenomonology:
Logic (as well as, for instance, mathematics and formal ontology) is not an empirical science and is not at all concerned with factually existing objects. On the contrary, it investigates ideal structures and laws, and its investigations are characterized by their certainty and exactness. In contrast, psychology is an empirical science that investigates the factual nature of consciousness, and its results are therefore characterized by the same vagueness and mere probability that marks the results of all the other empirical sciences (Hua 18/181). To reduce logic to psychology is consequently a regular category mistake that completely ignores the ideality, apodicticity (indubitable certainty), and aprioricity (nonempirical validity) characterizing the laws of logic (Hua 18/79-80). * These features can never be founded in or explained by reference to the factual-empirical nature of the psyche.
Why can't something like Logic be reduced to Psychological laws if it is something that originates from the brain? Even if Logic is capable of having apriori truths such as 1+1=2, isn't that still a process of the brain and subject to psychological study? Is Logic not built upon certain mechanisms within the brain? I am very confused on the argument against Psychologism.