Motion or change is simultaneously attaining something new and an action something is responsible for. In the first sense, something empty receives, in the second sense something full goes outside of itself like an overflowing cup. Both things are the subject, or the subject is both.
Motion is like a currency conversion from one of account to another one. Assume there is a dollar account and a Swiss Franc account (and that the currencies are 1:1) one account has 10 dollars, another has no Franks. Can I buy something that costs 10 Francs?
The same duality repeats itself in our ideas of cause, responsibility, desire, love, reasoning, time, creation.