He operates a great blog and has made himself known as a terrific Christian thinker in the blogosphere. In spite of that, some other bloggers think that blogging is all he is qualified to do, since Challies has no higher (Christian) education. Before I get into whether this is fair or not, I would like to point out that such questioning applies perfectly to me as well. So, whatever befalls Tim Challies in the numerous comboxes out there also sets a the temperature of my reception out in Christendom should I, too, write a book one day.
Compared to the average layperson in a similar lifestage to mine, my mainstage interests in theology and philosophy (and politics, I grudgingly admit) are unusual. Through NO church influence, I began studying Christian apologetics, culture, and theology at age 12. I became a believer in Reformed Theology at age 19, again, not as a result of any church/pastoral influence, but by the biblical and theological strength of Calvinism, aside from the divine conviction that this was so. But as a Calvinist, I would say such a thing, wouldn't I? :)
Now, as an adult, I find that that the God-given learning experiences I have diverge greatly from most other moms and homemakers. It's weird, because I don't see myself as being particularly different that any other SAHM with wee ones. But I'm blogging and reading Alister McGrath (if and when I can) when many of my mom-friends hardly know what blogging is and are reading, for lack of a better term, chick books (not that there's anything wrong with that...).
I have credibility and speak authoritatively on topics I know well to the people who know me. For Tim Challies, the situation is the same. Those who have endorsed his book know him and his strengths. They are confident enough in him as a Christian thinker to support him. As I see it, he fares much better than many a pastor who have written pure heresy (Benny Hinn, anyone?).
Blogger Mike Leake has blogged three considerations addressing credibility in the Christian world:
1) If they have an accurate Christology as clearly revealed in Scripture
then perhaps it is from God.
2) If their teaching sounds like the world, then it is not from God. (This is where the Osteen's and prosperity teachers fall off). If their teaching matches up to what is revealed in Scripture then it should be received.
3) What do trusted believers say concerning the matter?
Since the Holy Spirit dwells in believers and he confirms truth, what is the
consensus of godly men. Since this one is the most subjective it is the most
unreliable, but still should be strongly considered. Ultimately our trust in
discerning these matters should be in the Lord.
The rest of his post is great, so I highly recommend everyone to take a look.
Ultimately, credibility is found in the truth. Anything written, said, or implied by Christians as public message must correlate with Truth (with Schaeffer's capital "T"), whether it be Tim Challies, seminary students, or a humble homemaker like myself.
The thing I'd like to throw out there: Christian teachers and leaders aren't made, they're born (you might say reborn). The luxury of a seminary education may be out of reach or for some individuals. For others, seminary isn't a divinely appointed thing. In either case, formal Christian ed shouldn't be held as a prerequisite to the edifying of the Church.