I guess when I hear someone invoke the "law" of unintended consequences it's usually in a bad way. Like, "you can't go back in time and fix something because the chain reaction might blow up the world." But I think I very often find an upside to the "law" -- occasions where I do something (or someone else does) and years later something good results, totally unexpectedly. Case in point. I remember taking a statistics course in 2005, but only barely. That was a rough semester. I had to leave the house at 6:30 in order to make sure I made it to my 8:30 class, then I had a break before stats at 11:30 followed by a lunchless scamper back down I-45 to work. I'd get back around 2, meaning that between the classes I had 10 hours of work time to make up each week. Mid-way through the semester Kathryn got sick and ended up needing surgery, so I was pretty busy, and not well focused on the material. In addition, I was a bit disappointed because I had hoped the stats class would focus more on approximation theory and Gaussian models, and this didn't happen.
So fast-forward to this semester. I'm in another class, and we start talking about Poisson distributions and Markov chains. The professor is covering things in class in an intuitive way, generally glossing over the details, but giving homework questions that stress the theory. The textbook is next to useless - kind of a hybrid Math/Engineering book with scraps of random theorems thrown in presumably to make the book seem more rigorous. Tonight, I came across my notes from the stats class 3.5 years ago. And there they were. Poisson distributions. Markov chains. Probability theory. All explained in a beautifully concise and careful manner with plenty of intuition, summary and illustrative examples. How could I not have just eaten this up at the time? I guess I was too frazzled to appreciate it. But I sure do now! Thanks, Dr. Nicol. I owe you one.