It means you have to keep up with the science, even if your character still relies on psychology.

Behavioral psychology is the science of pulling habits out of rats.

The worst hidden in his character was ready to believe worst of everyone.

Human Psychology;Pity yourself if your mission is trying to understand another,for you can never truly understand any human,because every decade our character changes.

Science is as corruptible a human activity as any other.

Psychology is the Science of Mental Life, both of its phenomena and their conditions.