“If something can’t go on forever, it will stop.” — Herb Stein

When you think about it, we really do live in an age of miracles. Less than 24 hours ago, I was in London, but I slept in my own bed last night and am back at work in Boston today. While in Europe, I kept in touch with my family via video-call and simply pulled out my credit card to pay for things. It was all astonishingly seamless.

For the past two days, I’ve been in London at a J.P. Morgan European investment summit, and a fascinating time it has been.

As investors, it's not so much the things we don't know that we need to be mindful of, but the things we don’t even know we don’t know. For Americans, how things really are in the rest of the world can easily fall into that category, so it’s been interesting to get some international perspective over the last couple of days.

Here are three of my key takeaways.

One problem I have with satellite radio is that it makes me confront my own mortality every day. Let me explain. When a song comes on, I think, Oh, I remember that; it must have come out about five years ago. But when I look at the screen, the song is invariably from the 1990s or (in particularly bad cases) from the 1980s. Perhaps I’m not as young as I feel.

That said, a bit of perspective—which is a kinder word for age—is beneficial in the economics and investing game.

I’m currently reading Thinking, Fast and Slow by Daniel Kahneman—a great book on how we make decisions, and how we can learn to make better ones. Its assertions are shocking, and even insulting, but they’re all the more useful for it. (Look for a full review here soon.)

One of Kahneman’s points is how bad we are at remembering what we thought at a given time—and how we tend, in retrospect, to think we were much more prescient than we actually were.

As we discussed yesterday, economic slowing in the rest of the world, while certainly a headwind for the U.S. economy, isn’t really something to worry about. U.S. economic data—3.5-percent growth last quarter, plus another month of more than 200,000 jobs created—seems to support that.

But unlike economics, where U.S. exposure is relatively small, our political and institutional exposure is intense. Here are some examples of problems abroad that should seriously worry us. 

I’m going to take a chance—probably only a small one—and predict that the Federal Reserve will announce the end of its bond-buying program today.

If I’m wrong, I won’t be the only one. Expectations for the Fed to step back are almost universal at this point.

Over the past couple of years, we’ve seen government spending drop considerably as a percentage of the economy as a whole. But is it set for a comeback?

One way to get ahead of trends, in my opinion, is to take basic assumptions that everyone just knows are true and think about what the world would be like if, in fact, those assumptions turned out to be wrong. 

Since returning from the Goldman Sachs conference yesterday, I’ve been thinking about what was said there—as well as what wasn't so much said as assumed.

Looking at the data over the past few days, it’s apparent that the economy continues to improve. Consumer comfort is rising, initial jobless claims are up a bit but remain at extremely low levels, job openings are at multiyear highs . . . the list goes on and on.

This week’s market melt-up has been widely attributed to the release of the Federal Reserve’s meeting minutes. More or less, the Fed said it was worried about global growth and would probably be slower in raising rates than many had expected.

The effect on the market was substantial, which prompts a number of questions. But the one I want to talk about this morning is why the Fed is so worried.