primum mobile vs causal agent

primum mobile and causal agent both are nouns.

Word	Noun	Adjective	Verb	Adverb
primum mobile	Yes	No	No	No
causal agent	Yes	No	No	No

As nouns, causal agent is a hypernym of primum mobile; that is, causal agent is a word with a broader meaning than primum mobile:

primum mobile: an agent that is the cause of all things but does not itself have a cause
causal agent: any entity that produces an effect or is responsible for events or results

Other hypernyms of primum mobile include causal agency, cause.

primum mobile (noun)	causal agent (noun)
an agent that is the cause of all things but does not itself have a cause	any entity that produces an effect or is responsible for events or results