There is an old joke—so old, in fact, that it may be unknown to a newer generation and, therefore, recyclable.

A young farmer, standing in his field, observes a peculiar cloud formation. The clouds form the letters G, P, and C, and he thinks them a call from God: Go preach Christ!

The farmer rushes to the deacons of his church and insists that he has been called to preach. Respectful of his ardor, they invite him to fill the pulpit.

That Sunday, the sermon is long, tedious, virtually incoherent. When it finally ends, the leaders sit in stunned silence. Finally, a wizened deacon mutters to the would-be preacher, "Seems to me the clouds were saying 'Go plant corn.'"

If it really happened that way, it wouldn't be the first time there's been confusion about what it means to be called into ministry.

The concept of a call is one of the most profound of all biblical ideas. The Bible is riddled with stories about calls to men and women who, when summoned to service, went out and marked their generation ...