In a recent interview (all of which is worth reading), the Internet Monk asked Dr. Michael Wittmer (author of one of my favorite books, Heaven Is A Place On Earth: Why Everything You Do Matters To God) a great question about vocation:
How would you counsel someone who said they were changing their major from engineering to theology because they wanted to glorify God with their lives?
I would inquire about their motivation. Do they think they will glorify God less as an engineer? If so, they don’t understand the Christian worldview. Every so often I meet students who come to seminary from this wrong, Platonic motivation. Actually, it’s a big reason why I decided to enter the ministry when I was in high school. So God can use wrong motives for good, but it’s best to clear this up, as I do with my students, and assure them that they may well bring glory to God as a pastor, but they may bring him just as much glory in a secular field. I teach them to find their calling by asking What am I good at?; What do I enjoy doing? And what does the world need? If you can find where these lines intersect, you can know that whatever you do is a calling from God, whether that is preaching a sermon or drawing a blueprint.