"I hear the voice of the Lord, saying: 'Whom shall I send, and who will go for us?' Then I said, 'Here am I! Send me' " Isaiah 6:8
God did not direct His call to Isaiah - Isaiah overheard God saying, "...who will go for Us?" The call of God is not just for a select few but for everyone. Whether I hear God's call or not depends on the condition of my ears, and exactly what I hear depends upon my spiritual attitude.
God doesn't single out someone and say, "Now, you go." He did not force His will on Isaiah. Isaiah was in the presence of God, and he overheard the call. His response, performed in complete freedom, could only be to say, "Here am I! Send me!"-Oswald Chambers
Wow - what more can I add? May my heart always be tuned in to hear that Voice, and my life ready to follow whatever the cost may be!