There’s nothing quite like a good metaphor. A powerful metaphor realigns ideas and experiences as surely as a powerful magnet realigns iron filings and sometimes just as quickly.

I teach a series of classes on ancient narratives from other cultures.[1] It takes up most of my time for most of the weeks of the year. I love it. It requires a good deal of academic study for reasons I will describe shortly. It requires all the pedagogical ingenuity I have been able to assemble in a career of teaching that has lasted over 60 years so far. It is frustrating and exhilarating and some weeks it takes all I’ve got. I love it.

This morning, when I got up, I realized that some time during the night I had found another way to deal with a problem in Luke 17:10, in which Jesus seems to be saying that regarding ourselves as “unprofitable” slaves of God is the attitude we ought to aspire to. When I was awake enough to realize what had happened, I got out of bed with some enthusiasm (not the way I always get out of bed) and started writing.

My son Dan, when we met for coffee last week, called that collection of experiences—the classes and the instant realizations— my whetstone. And he knows what he is talking about. Most of the classes are on Thursdays and Dan and I meet on Fridays. On good weeks, I am flying high and want to tell him what went unexpectedly well. That’s how he knows what he is talking about. But he also knows what it costs me to teach those classes and that’s what he captured in the whetstone metaphor.

“I think it’s what keeps you sharp.” he said.

The whetstone metaphor takes seriously the abrasion that occurs as I prepare and teach these courses. I don’t experience that abrasion, myself. My attention is elsewhere, like the puzzling word in Luke 17:10 (“unprofitable”), or like how to elicit from the members the discipline that will allow us to pursue the same project together. Discipline is required because as we discuss, hundreds of related ideas occur. It takes a presence of mind and a willingness to postpone the rush of a new and sometimes very personal idea. That’s the source of some of the abrasion I experience as we study together.

And then, some members of these classes like to argue with me just because they like to argue. I like that too, but arguing with them because I don’t want to lose the argument is the wrong kind of abrasion. Metaphorically, I am holding the knife blade at the wrong angle to the stone. Arguing for a better frame of reference—one that will continue the argument along useful lines and may very well invite others to join in it productively—that is what holding the knife at the right angle looks like.

Similarly, some topics present difficulties that can be resolved by any one of a number of intellectual shortcuts. This is a challenge I face as I am preparing for the classes. If I want the students to approach the texts in a scholarly way, then certainly I need to approach them in a scholarly way. I need, for instance, to work with the most likely meaning of a text, rather than the meaning I would be most comfortable with. The abrasions I experience in setting aside my preferences and focusing instead on the most likely meaning are the kind that will keep me sharp.

Not pursuing my preferences feels like work some days, but if it helps keep me sharp, it is well worth it. And a good metaphor is a treasure.

[1] They are actually Bible studies, but in trying to explain what they are and how they work, I have learned that once I use the expression “Bible study,” most people stop listening, believing that they already know what kind of learning project I am talking about. They don’t.