No. A leaf blowing off a tree doesn’t have to understand causal relationships. There is action (i.e. activity) taking place there. Just not human action (i.e. purposeful means to achieve an ends).
Yeah basically. Because if you didn’t understand the existence and reality of cause and effect, you wouldn’t be able to act with purpose…meaning any activity that did take place would be completely random and without purpose. The whole point of praxeology (or, perhaps more accurately, the cornerstone) is that “humans act”…as in, human beings have desires they wish to fulfill, and through their understanding of causal relationships they use “means” (action) to achieve their desired “ends” (effects).
What Mises is trying to get across is that before this purposeful action can take place, the actor must recognize causal relationships.