an agent whose particular effect is concomitant with it (1), whether it is termed an efficient [cause] or not (2). It is, however, conceivable for a condition to be concomitant with that which it conditions.

[The Correct Meaning of Priority and Posteriority]

The example (3) they cite—saying, “I moved my hand, whereupon my ring, my sleeve (4), or the key (5) moved,” and the like—is evidence against them, not for them. The movement of the hand is neither the complete cause nor the agent responsible for the ring’s movement. [Rather, the ring] (6), in relation to the finger, is like the finger in relation to the palm. The ring is connected (7) to the finger, and the finger is connected to the palm. The ring, however, can be removed without pain, unlike the finger, and a slight gap may arise between the finger and the ring (8), unlike between the constituent parts of the palm.

The movement of the finger is nevertheless a condition for the movement of the ring, just as the movement of the palm is a condition for the movement of the finger—that is, for the particular movement that originates in the hand. This is in contrast to a movement that begins in the ring or the finger itself, for this movement [extends] (9) from it to the palm, as when someone pulls another person’s finger and thereby pulls his palm along with it.

As for their assertion that priority and posteriority occur by essence and cause, as in the motion of—