God cannot use people who are full of themselves. He prefers empty vessels. Why did Jesus choose fishermen to be His inner circle? Same reason. They were not prominent, highly gifted, or wealthy. They were perfect candidates for Jesus to mold into the leaders He needed them to be. My take on God’s choice of Moses is that Moses’ ego was not going to get in the way. God knew that Moses was up for the selfless task of leading God’s people on a very difficult journey. I think a whole lot of very gifted