Activity from adequate ideas; passivity from inadequate ideas
Formal Statement
Our mind is active insofar as it has adequate ideas, and passive insofar as it has inadequate ideas. The activities of the mind arise solely from adequate ideas; passive states depend solely on inadequate ideas.
In Plain Language
Here is the master distinction for everything that follows. When you truly understand something — grasping its cause clearly — you are the adequate cause of what follows from that understanding. You are active. When your ideas are confused fragments that depend on external things you don't grasp, you are merely a partial cause. You are passive, pushed around. Emotions will split along exactly this line: some will be things that happen to you, others will be things you do.
Why This Follows
The mind's essence is constituted by adequate and inadequate ideas (ce-02, II.P11, II.P13). Whatever follows from an adequate idea has the mind as its adequate cause (III, Definition I–II). Whatever follows from an inadequate idea has the mind as only a partial cause. So the active/passive boundary maps directly onto the adequate/inadequate boundary.
The active/passive distinction in emotion tracks the adequate/inadequate distinction in cognition.
Connected Concepts
Can you think of an emotion you have felt that seemed to arise from genuine understanding rather than confusion? What made it different?