There were four fundamental loyalties in the Irish working-class neighborhood around 80th and South Park where my father grew up: the Catholic church, the Democratic Party, Notre Dame football, and the Chicago White Sox.

My dad is a true Sox fan–he feels his duty is not only to root for his team but also against the Cubs. He immediately came to mind when I scored tickets to the final contest in last year’s crosstown series with less than 48 hours till game time. I figured he’d jump at the chance to see the Sox, then riding high, prove their supremacy.

Guess again. “But it’s at Wrigley,” he protested.

Dad, then 62, hadn’t set foot in Wrigley Field for nearly five decades. Almost all of his adult life had been spent within 90 minutes of Clark and Addison, but he never found a reason to go to the park–not curiosity, or variety, or joining a friend who had tickets. It took a little prodding before he relented. He agreed to go only for the chance to spend time with me.

Attending ball games was a treasured part of dad’s relationship with his own father, so he too raised his kids to be Sox fans. I remember a Friday night game in 1983 at old Comiskey, sitting in the left-field grandstands with my brothers and sister. The Sox were breaking the division race wide open, and by about the seventh inning the game was well in hand and the crowd well lubricated. The stadium rocked. Dad turned to me and said, “Pennant fever, catch it.”

It was thrilling. Our team seemed on the verge of going all the way, though it was not to be, of course. Later a new and stronger Sox were in first place when major-league ballplayers went on strike August 12, 1994. Jerry Reinsdorf was fronting the hard-line owners, and he let go of solid Sox players, mistakenly assuming there would be no season in ’95. Then in 1998 Reinsdorf decimated the Bulls too, and I decided it would be OK to stray.

Living on the north side, I got caught up in the enthusiasm as Sammy Sosa and Mark McGwire vied for Roger Maris’s home-run crown and the Cubs squeaked into the playoffs. For one shameful half season, I became a fair-weather Cubs fan. No sooner had the Braves swept the Cubs out of the playoffs than I was on the phone to dad, beginning the conversation like a prodigal son: “Forgive me father, for I have sinned.”

My dad grew up in a time of certainties. No matter how much the world changed–from Veeck to Reinsdorf, Kennedy to Clinton–he kept the faith. I was born into a world with few acknowledged truths, where people base their choices on what makes the most sense at a particular moment. In my father’s devotions, I see both loyalty’s price and its inherent value. Sometimes keeping a commitment–to a team, a cause, or a person–defines you in ways that are more important than the short-term benefits of convenient options.

So dad wasn’t just being ornery when he decided to buy a T-shirt that said “Cubs Suck” as we approached Wrigley. If he was going to be in the enemy camp, he wanted to make clear which side he was on. “I feel like I’m committing treason,” he muttered as we walked into the friendly confines.

It came as no surprise that Dad didn’t like Wrigley. Never mind the ivy–the men’s room is too far away. And see those girders supporting the upper deck–they’re blocking the view. Whatever its faults, Comiskey Park offers unobstructed sight lines. “The Sox even have better suites,” he declared.

He moved on to bad mouthing players, like a married man trashing another guy’s girlfriend. He called Mark Grace “average” and found it disgraceful that the Cubs were still capitalizing on Harry Caray after his death. During the seventh-inning stretch Donald Trump rose to deliver a tuneless rendition of “Take Me Out to the Ballgame.”

“The Sox would never do something like this,” Dad said, pointing to Trump. “They play in a working-class neighborhood–they would have lynched him.” Despite his doctorate in political science and a university pension that allowed him to take early retirement, my father remained a class warrior.

The Sox were leading 6-5 in the bottom of the sixth when a Cubs rally put the north-siders up by one run. Dad stepped behind a beer line to put on his T-shirt. Within minutes, disaster struck. Ex-Sox Sammy Sosa hit a two-run homer, and the Cubs were on top to stay, 9-6.

“This is your fault,” dad said afterward. “I never should have let you bring me here.” I knew he was kidding, but I was disappointed I’d taken him to a losing game. Once again the Sox had let us down.

Walking back to our car, dad maintained the same opinivonated manner that’s charmed, frustrated, and influenced me my entire life. I’d hoped the outing would bring us closer, but the afternoon brought no change, just a Sox loss in Wrigleyville. We stopped at a Starbucks and on our way out passed a pretty young woman talking on a cell phone. She looked at my father. “Great shirt,” she said.