“Joy is man's passage from a lesser to a greater perfection.”Baruch Spinoza · Etica · 1677 · Partea a III-a, definițiile afecțiunilor, definiția 2
Joy is not a prize you receive, but the feeling of your own power growing.
Spinoza defines emotions through the movement of one's power to exist: when that power grows, we feel joy; when it shrinks, sadness. Joy is therefore never passive, but a sign that you are becoming more capable. When you learn an instrument and manage to play a whole piece for the first time, the joy comes not from applause but from being more than you were yesterday.
If joy signals a growing power, then sadness becomes a useful clue, not an enemy. It shows you that something in your life is lowering your capacity to act. A friend who leaves you drained and doubting after every meeting is telling you something through the feeling they leave behind. Spinoza does not say to flee sadness, but to read it as a signal pointing toward its cause. The next step is to see why our emotions are almost always mixed, never pure.
Why it matters It helps you choose activities by their real effect on your power, rather than by short pleasures that drain you.