meaning - semantic difference for the forms: "x of y" vs. "x of the y" vs. "y x"

As a non-native speaker, I have a problem understanding the difference in meaning of the following forms:

• "… of …"


• "… of the …"


• "… …"

To be more specific, let me give some instances:

• "theory of mind" vs. "theory of the mind" vs. "mind theory"


• "theory of activity" vs. "activity theory"


• "theory of action" vs. "action theory"

While writing, I naïvely notice that there is a difference in nature between my first example and the two latter… I fail to understand exactly why, either… I don't know why, but while "theory of the mind" sounds understandable to me, "theory of the activity" or "theory of the action" sounds less correct (maybe because we can speak about "the mind" as a generality, while "the action" or "the activity" needs to be specified?).

Any help would be much appreciated,

Many thanks

Answer

You are astute in observing the subtle difference with "mind". I think you got that right.

As for the others, there is a slight connotative difference between, say, "theory of action" and "action theory". The first is clearly a theory about action and its causes. The second might be proposing "action" as an explanation or cause of something else.

Consider, for example, Brown's motion theory (or rather Einstein's motion theory, as borne out by Brown's experimental observations) which is now accepted as an explanation for how temperature change "works".