Natural science, including psychology, attends exclusively to external features, which are objectively describable and measureable from a third-person perspective.

It progresses because it explains the relations of this complex and shifting world to a refutable number of laws. It is a process that allows us to make some sense of the complexity.

For example: An emotion wouldn't be treated as a subjective experience emenating from a first-person persepctive and related to a meaningful context, but rather as a purely external reality to be desrcribed in a way that is completely void of internl considerations of subjectvity, meaning or value.