Albert Barnes Commentary 1 Corinthians 12:19

"And if they were all one member, where were the body?" — 1 Corinthians 12:19 (ASV)

And if all were one member. If there were nothing but an eye, an ear, or a limb, there would be no body. The idea which this seems intended to illustrate is that if there were not a variety of talents and endowments in the church, the church could not itself exist. If, for example, there were nothing but apostles, or prophets, or teachers; if there were none but those who spoke with tongues or could interpret them, the church could not exist. A variety of talents and attainments in their proper places is as useful as are the various members of the human body.