Gerald Hiestand and Todd Wilson give three reasons for a pastor-theologian to get a PhD. This is from their book The Pastor Theologian: Resurrecting an Ancient Vision (Grand Rapids: Zondervan, 2015), 104–5:

Strategy One: Get a PhD

We begin with this not because it is the most important strategy, but because it is a critical part of the preparation we believe is necessary for ecclesial theologians. The costs of a PhD—financial, emotional, familial—are significant and not to be taken lightly. For some, a PhD may not be possible or prudent. Yet those who aspire to be ecclesial theologians should think seriously about pursuing a PhD. True, Karl Barth didn’t have PhD. But until you’ve written something remotely akin to his Römerbrief, you should probably get on with getting one; it will almost certainly be necessary for pursuing the sort of vision we’ve laid out for the ecclesial theologian. We say this for at least three reasons.

1. Training. The PhD offers a regimen of disciplined training that would be very difficult to get independently. Despite the limitations of social location, academic scholars know their business, namely, research. The task of the ecclesial theologian will likely be less focused research than that of an academic scholar; yet locating and properly handling primary and secondary sources is vital to the work of the ecclesial theologian, and academic theologians are best positioned to provide tutelage in this area. To be sure, the theological method of the academy is not always congruous with the theological method we envision for the ecclesial theologian. And in this sense, pursuing a PhD as training for becoming an ecclesial theologian may be a bit like a long-distance runner training for a triathlon; it won’t be an exact match. But at present, the academy is still the best training out there for acquiring the sort of research competency we envision being necessary for ecclesial theologians. This competency and experience can be accomplished in limited measures through an MA or an MDiv; but anyone who has done a PhD will tell you that the requirements of a postgraduate research degree push beyond anything seen at a graduate level.

2. Networking. Working on a PhD will broaden your network of relationships with other thinkers and scholars, particularly with academic theologians. In keeping with our comments in the previous chapter, your ongoing work as an ecclesial theologian will need to be carried out in partnership with academic theologians. Involvement in a PhD program helps to establish relationships with other scholars—both ecclesial and academic—and connects you to networks that won’t otherwise be accessible. As a pastor doing theology, these relationships and networks are vital, insofar as they are no longer readily available in your pastoral vocation.

3. Publishing. The PhD remains the intellectual’s best calling card. Resist it as a pretentious, elitist social construct, but there it is all the same. And truthfully, a PhD demonstrates that one has at least a modicum of intellectual firepower, as well as the work ethic necessary to see a serious intellectual undertaking all the way through to completion. There are other intellectual calling cards, of course, but a PhD will help open doors for you in terms of scholarship and publication that would otherwise require more vigorous knocking. This is not to say that publishers will certainly look at your manuscript because you have a PhD or that they will certainly reject your book proposals because you don’t. But it is to say that having a reputable PhD at least earns you the benefit of the doubt. This is all the more important given the fact that your vocation as a pastor will bring with it assumptions about your intellectual caliber that may tend in the opposite direction.

On the other hand, contrast John Piper’s advice in this 3.5-minute video: “Should Pastors Get PhDs?” (DesiringGod.org also includes a transcript of the video).

https://vimeo.com/47573807

I’m sympathetic with Piper’s argument. Is a PhD necessary for a pastor? Of course not. But helpful? A wise PhD is. Here’s how Piper puts it:

If a PhD program is set up—and there are some!—to really let you work on the Bible for three or four years and on understanding its larger implications for life and reality, then, on your way towards the pastorate, that could be gold.

Also, at the very end of the above video, Piper concedes, “Maybe that’s an overstatement.” He is answering the question based largely on his doctoral experience in Munich, Germany. In contrast, I had very positive doctoral experiences that focused on sound exegesis and theology.

Dane Ortlund shrewdly responds to Piper: “Stupid PhDs vs. Wise PhDs.” Amen.

(The last thing I want to do is suggest that pastors without PhDs are inferior. The target audience I have in mind is seminary students working on an MDiv or ThM who want to be pastors and are wrestling with whether it is worth the time and effort to earn a PhD.)

Related:

1. Eric Ortlund, “Things I Wish I Could Say to Evangelical Students Beginning Their Doctorates”
2. Rusty Osborne, “PhDs Build Character More than Careers“
3. John Stackhouse Jr., “Thinking about a Ph.D.?“
4. Should You Be a Pastor or a Professor?
5. 3 Reflections on Evangelical Academic Publishing

Update:

1. Tom Schreiner, “Pastor or Scholar? Pursue Your Strongest Desire,” The Gospel Coalition, November 3, 2015.
2. Andy Naselli, “Advice for Students Considering a PhD,” April 11, 2017.
3. Todd Chipman, “To Ph.D or Not to Ph.D?,” April 24, 2017.
4. Sequeira, Aubrey M., James M. Hamilton Jr., Jonathan Leeman, Matt McCullough, and Thomas R. Schreiner. “Forum: Do Pastors Need a PhD?” 9Marks, 16 November 2021.