In the wrong hands, sweater vests happily fail. During the last primaries, Rick Santorum, US presidential hopeful and vest enthusiast, demonstrated this principle masterfully, even hocking a limpid version embroidered with his campaign logo in a late effort to raise critical funds. It, and he, failed; irony is just not the stuff from which presidents are made. I must confess that this particular stunt offended far more than the typical ribbing that ordinarily clings to sweater vests and their advocates. I often wear them and have grown accustomed to the occasional gibe, but any attempt at marginalizing this practical garment as mere costume cuts too deeply.

Sleevlessness alone isn’t the problem: down vests, waistcoats from three-piece suits, flak jackets—these don’t attract ridicule like their knit cousins. In truth, the opposite is true as the above examples are the stuff of adventurers, power brokers and soldiers. At best a sweater vest is tidy, at worst, a signifier of a stock nerd—an instant Steve Urkel or Rick Moranis. This isn’t accidental though. Nerds are nothing if not practical, and the sweater vest really is a remarkably practical thing.

The reasons why are both demonstrable and metaphysical. Layered dressing works well because each successive layer of clothing multiplies the air pockets that aid in insulating the body. Unlike one heavy layer, several lighter layers can be shed or added as need arises. The problem is wearing several layers can feel restrictive, especially though the shoulders and arms. By eliminating sleeves, a sweater vest can comfortably reside between shirt and jacket, insulating the torso while leaving the major joints free to comfortably operate.

But there is more to a sweater vest than common sense. A day spent in one provides a difficult to categorize experiential aspect. Freedom of movement is important, as is insulation of the core, but the sum is somehow greater than the parts. I suspect it makes the wearer feel clever for having been practical. This is especially the case when it comes to travel. Here sweater vests really shine, from the dramatic temperature differences between cabs, terminals and cabins to the greatly reduced space they seem to require in a case. When packing room is limited, a sweater vest also seems to multiply looks; a navy blazer or tweed coat gains new life once a characterful sweater vest is slipped beneath.

As is so often, the intersection of practicality and versatility is also the entry point for style. The wearer is inevitably a thinking man, but not one so fastidious as to be concerned with the potential of looking a tad square. He instead dabbles equally in fair isle and argyle, camel hair and cashmere, unconcerned that one or the other might disrupt some meta-harmony of an otherwise restrained composition. He might even be considered louche. But, importantly, he's also warm around the middle.