A.T. Robertson Commentary 1 Corinthians 12:21

"And the eye cannot say to the hand, I have no need of thee: or again the head to the feet, I have no need of you." — 1 Corinthians 12:21 (ASV)

Cannot say (ου δυνατα ειπειν). And be truthful. The superior organs need the inferior ones (the eye, the hand, the head, the feet).