This has been the summer of the recidivist. Politicians, athletes, Wall Streeters: No one ever learns their lesson. Over the last two weeks, the newspapers of New York City have been filled with stories about Anthony Weiner, a repeat sext offender; Stevie Cohen, a repeat insider-trading offender; Tyson Gay, the latest track and field steroid offender; and Alex Rodriguez, a lifelong offender of baseball fans everywhere.

In the New York Times this morning, the story about Cohen and his recently indicted hedge fund, SAC, is placed right next to the story of Fabrice Tourre, a former trader at Goldman Sachs who was found liable of fraud yesterday in a case stemming from the financial crisis of 2008. Remember the phony ratings and subprime mortgages that got us into so much trouble that time? Believe it or not, they’re back, too. “Five years after inflated credit ratings helped touch off the financial crisis,” the Times reported last week, “Standard & Poor’s has been giving higher grades than its rivals to mortgage-backed securities as Wall Street is eagerly trying to revive the market for these investments.”

You may look at all of this and ask, “Why are you surprised?” It’s true, lying and corruption weren’t invented in the last five years. But it does feel like, from government to business to sports to public figures in general, there’s less to believe in than ever. Maybe that’s just an inevitable result of growing up: You start to suspect that there are no standards, there is no code, and that cheating pays. There isn’t even honor among thieves, as another summer story has shown us in gory detail. During his trial in Boston, we’ve been reminded that mob boss Whitey Bulger wasn’t just a cold-blooded killer, he was a rat for the FBI, too.

For the last few weeks, I’ve followed these stories while waiting to get on court at my tennis club. The sport is, or once was, famous for its code of honor. That’s even the name of the guide that the USTA publishes for unofficiated matches: The Code. Is the tennis court still a refuge for sportsmanship? That depends on who's playing on it, of course. But this summer I’ve come to think that tennis offers a unique and important opportunity for honesty.

We talk a lot about how sports builds character; that’s usually seen through the lens of winning and losing, and learning to “treat those two impostors just the same.” Tennis teaches those lessons as well. Equally important, though, it's a sport that forces its players to do their own umpiring, even in organized competitions. Organized team sports come with a ref who renders judgments and keeps everyone in line. In tennis, unless you’re a pro, you and your opponent are on your own. This is true from the first time you pick up a racquet as a junior, to the last time you put it down as an adult.

As I said, how honest any player is depends on the individual. I’ve strayed from the code myself. In a 14-and-under doubles match, I watched as a crucial shot by one of my opponents landed inside the baseline for a winner. Then I watched as my partner confidently stuck his index finger in the air and shouted, "Out!" My partner’s reputation for unfairness preceded him, so both of our opponents immediately appealed to me—Come on, Steve, you know that was in.”

I did know it was in, but I didn’t tell them that. “I didn’t see it,” I said, after a pause. Not surprisingly, they didn’t buy my answer, and the argument quickly escalated. After much pointing and whining, we finally called down the tournament director, who put a rapid end to the situation. He gathered the four of us around him, turned briefly to make sure no parents were listening, and said, “You little babies better get back out there and play or I’m going to beat the s**t out of all of you.”

We put our heads down and did as we were told; anyone watching must have been amazed at how amicable our match suddenly became after that. Still, the tidy end to our spat didn’t provide an answer to my problem, a problem that can crop up in any unofficiated doubles match: If you see your partner cheating, do you contradict him and tell the truth to your opponents? Or do you stand by him? The Code, naturally, sides with the truth, but the reality of the situation will often be more complicated. Your doubles partner, while the two of you are on court, is a fellow soldier, a brother in arms. Rather than the code of transparency, brothers and soldiers tend to live by the code of silence. At 14, I went with silence.

It didn’t get better after that. A couple of years later, I played a tournament that was mostly stocked with college players. I lost to one of them, and got a bad call along the way. Afterward, I was talking to an older player about it; when I brought up the call, he gave me this piece of wisdom: “In college, half of the line is out.” Later I discovered that while that wasn’t literally true, he did have a point. In college, if there was any doubt about where a ball landed, few players were going to give, or get, the benefit of it. You have to do what you can for your teammates, right?

But that’s what makes tennis a valuable test of honesty: It’s hard. The temptation to cheat is real. If you have a break point, and your opponent’s forehand catches the back of the baseline, it’s just as easy to call the shot long, pick up the ball, and start serving the next game. No one will know the difference, and by the end of the match even you will probably have forgotten your little moment of evil. By being honest, you’re fighting against your own will to win.

I was reminded of the power of that temptation, and that will, earlier this summer. It was late in the afternoon at my club, and there was no one else on the courts other than my opponent and I. My competitive juices ebb and flow depending on the day and the opponent; some days I care, other days I don’t. On this day, despite the fact that we were playing a meaningless pickup match, I definitely cared. I had been ahead, my opponent had come back, and I didn’t want to blow the set—it’s choking, more than losing, that I can’t stand now.

On a key point late in the second set, I hit a good serve that I thought was going to be an ace. He stabbed a return back that floated high and deep. So deep that I thought it might land long. I hoped it would land long, anyway. I hoped hard enough that when the ball finally touched down in the middle of the baseline, I felt a tiny desire to call it out anyway. It wasn’t a temptation; I was never going to cheat in a weekend pick-up match against a friend. Yet it didn’t change the fact that, a few seconds earlier, I thought I had the point won, and I was infuriated to have to start it over and possibly lose it. I really wanted that ball to be out.

And for good reason. I eventually lost the point, lost my serve, and lost the set. But as corny as it may sound to say in a summer like this one, the summer of the repeat cheater, it felt good to make the honest call—just as good as it would have felt if the ball had been long, and I had gone on to win the match. Tennis can still teach you that.