I'm four beers into a six-pack I started drinking four hours ago.

I'm not drunk, and I'm not bored with this beer, either.

It's what you call a session beer — something that's not so high in alcohol or so intense in flavor that it pickles your liver or exhausts your taste buds.

What's a good session beer? Depends on whom you ask.

For the casual drinker who just wants to have something cold in hand throughout a tailgate party, something like Bud Light very well may be ideal.

It's not going to fill you up, it's certainly not going to overwhelm you with hops and, at 4.2 percent alcohol by volume, it's not going to inebriate you unless you're chugging beer after beer.

I spent my formative drinking years thinking Pennsylvania's Yuengling Lager was the best session beer around. It's cheap, it's 4.4 percent ABV, and it goes down cold and smooth. But moving to St. Louis and seeing what the craft-brew industry has to offer, I realize that my beloved Yuengling is a really only a small step up from the Bud Lights of the world.

A truly good session beer needs to have enough flavor to keep things interesting throughout the session, be it an afternoon watching a ballgame or a night at a pub.

For me and, I suspect, most beer drinkers, I usually mix things up, trying a few different beers throughout a session. So if I'm going to stick with one brew, it should be balanced in its hops and malts, with a crisp, dry finish that leaves me wanting another sip.

The great beer writer Stan Hieronymus compares session beers to chameleons.

"We want a little color and excitement, but it should spend most of its time blending in," he says. "Something there when you look, but otherwise in the background."

When I ask for his favorites, Hieronymus mentions Unfiltered Wheat from Kansas City's Boulevard Brewing Co., giving it points for its lower (4.6 percent) alcohol content, and Schlafly's Kolsch. He says both are beers that "you can find something interesting in but don't demand attention."

Ryan Heinz, a spokesman at University of Missouri-St. Louis, says that, like me, he prefers beers that are either hoppy and bitter or dark and heavy.

"Naturally, that doesn't lend to much of a long session before the ol' taste buds start to fry," he says.

When he's looking for a beer to keep things interesting over the course of a session, Heinz turns to Mothership Wit, an organic wheat beer from Colorado's New Belgium Brewing Inc., or O'Fallon Gold, a blond ale from one of our backyard breweries.

Session beers don't have to be boring or mass-produced, and they don't have to be limited to a particular style. You can find porters and stouts, brown ales and pale ales, and lambics and saisons that are sessionable.

The important thing is that you find something that you like enough to keep going back to, and something that isn't so high in alcohol that you can't read the label after the second bottle.

So what's been my session beer today?

New Belgium's 1554 Enlightened Black Ale. Here's proof that dark doesn't necessarily mean heavy when it comes to beer. This Belgian dark ale is sessionable for sure. It's my go-to beer when I'm watching football on an autumn Sunday.

It toes the line of alcohol content for a session beer at 5.5 percent, but if you space it out and complement it with, say, pizza, 1554 gives just enough flavor to leave you wanting more, without making you reach for a bottle of aspirin at the end of the night.