It would seem that one can pursue any science with the intellect alone except psychology, whose subject—the psyche—has more than the two aspects mediated by sense-perception and thinking.
The function of value—feeling—is an integral part of our conscious orientation and ought not to be missing in a psychological judgment of any scope, otherwise the model we are trying to build of the real process will be incomplete.
Every psychic process has a value quality attached to it, namely its feeling-tone.
This indicates the degree to which the subject is affected by the process or how much it means to him (in so far as the process reaches consciousness at all).
It is through the “affect” that the subject becomes involved and so comes to feel the whole weight of reality.
The difference amounts roughly to that between a severe illness which one reads about in a textbook and the real illness which one has.
In psychology one possesses nothing unless one has experienced it in reality.
Hence a purely intellectual insight is not enough, because one knows only the words and not the substance of the thing from inside. ~Carl Jung, CW 9ii, Para 61