I’ve been thinking about the transitive—or is that intransitive?—power of similarity. Specifically, about two years ago, I met a woman who very strongly reminds of another I’ve known for a very long time. They have completely different personalities, so there’s no chance of confusing one for the other, but they look so similar that one might think them sisters.

About a year ago, I mat a third woman who very strongly resembles the second. Again, different personalities, quite clearly different people, but a very similar look.

However, the third woman in no way reminds me of the first. I’m confused. The second woman I met reminds me so strongly of the first that whenever I see her, I do a double-take to confirm her identity. And the third, again, is an equally close match for the second. But whenever I see the third, I can see no similarity with the first.