A clever man commits no minor blunders.

Small mistakes spiral into everything

There's a sharp observation hiding in this line that goes beyond just saying "smart people don't mess up." Doyle is pointing out something about how intelligence actually works in practice: clever people understand that small mistakes compound. They know that a tiny oversight—forgetting to check a detail, letting a small lie slide, skipping one step in a process—can spiral into something much worse. So they're ruthless about the little things precisely because they can see where carelessness leads.

This matters now more than ever, in a world where we're all juggling so many small decisions. We tend to think intelligence is about handling the big moments, but the real test is whether someone sweats the details most people ignore. A clever person doesn't think "nobody will notice if I cut this corner"—they think "what goes wrong if I do?" It's the difference between being smart and being wise. The slightly counterintuitive part: this mindset isn't actually about perfectionism or anxiety. It's about respect for how systems work. The clever person respects the machinery enough to know that every part matters.