Quote I’m reminded of, from Matthew Crawford’s Shop Class as Soulcraft—long but I think worth reading:
Following graduate school in Chicago, I took a job in a Washington, D.C. think tank. I hated it, so I left and opened a motorcycle repair shop in Richmond. When I would come home from work, my wife would sniff at me and say “carbs” or “brakes,” corresponding to the various solvents used. Leaving a sensible trace, my day was at least imaginable to her. But while the filth and odors were apparent, the amount of head-scratching I’d done since breakfast was not. Mike Rose writes that in the practice of surgery, “dichotomies such as concrete versus abstract and technique versus reflection break down in practice. The surgeon’s judgment is simultaneously technical and deliberative, and that mix is the source of its power.” This could be said of any manual skill that is diagnostic, including motorcycle repair. You come up with an imagined train of causes for manifest symptoms and judge their likelihood before tearing anything down. This imagining relies on a stock mental library, not of natural kinds or structures, like that of the surgeon, but rather the functional kinds of an internal combustion engine, their various interpretations by different manufacturers, and their proclivities for failure. You also develop a library of sounds and smells and feels. For example, the backfire of a too-lean fuel mixture is subtly different from an ignition backfire. If the motorcycle is thirty years old, from an obscure maker that went out of business twenty years ago, its proclivities are known mostly through lore. It would probably be impossible to do such work in isolation, without access to a collective historical memory; you have to be embedded in a community of mechanic-antiquarians. These relationships are maintained by telephone, in a network of reciprocal favors that spans the country. My most reliable source, Fred Cousins in Chicago, had such an encyclopedic knowledge of obscure European motorcycles that all I could offer him in exchange was regular shipments of obscure European beer.
There is always a risk of introducing new complications when working on decrepit machines, and this enters the diagnostic logic. Measured in likelihood of screw-ups, the cost is not identical for all avenues of inquiry when deciding which hypothesis to pursue. For example, the fasteners holding the engine covers on 1970s-era Hondas are Phillips-head, and they are always stripped and corroded. Do you really want to check the condition of the starter clutch, if each of ten screws will need to be drilled out and extracted, risking damage to the engine case? Such impediments can cloud one’s thinking. Put more neutrally, the attractiveness of any hypothesis is determined in part by physical circumstances that have no logical connection to the diagnostic problem at hand, but a strong pragmatic bearing on it (kind of like origami). The factory service manuals tell you to be systematic in eliminating variables, but they never take such factors into account. So you have to develop your own decision tree for the particular circumstances. The problem is that at each node of this new tree, your own, unquantifiable risk aversion introduces ambiguity. There comes a point where you have to step back and get a larger gestalt. Have a cigarette and walk around the lift. Any mechanic will tell you that it is invaluable to have other mechanics around to test your reasoning against, especially if they have a different intellectual disposition.
My shop-mate Tommy Van Auken was an accomplished visual artist, and I was repeatedly struck by his ability to literally see things that escaped me. I had the conceit of a being an empiricist, but seeing things is not a simple matter. Even on the relatively primitive vintage bikes that were our specialty, some diagnostic situations contain so many variables, and symptoms can be so under-determining of causes, that explicit analytical reasoning comes up short. What is required then is the kind of judgment that arises only from experience; hunches rather than rules. There was more thinking going on in the bike shop than in the think tank.
Quote I’m reminded of, from Matthew Crawford’s Shop Class as Soulcraft—long but I think worth reading: