Yesterday, I was interested in a paper because I was interested in that paper. Here's the story. I was interested in a paper by John Norton. A colleague mentioned that he had come across a paper and described the topic it was on. It was closely related to the topic of the paper that interested me, and hence I became interested in the paper that the colleague had come across. However, as it turned out, it was the same paper, though in a revised version.
Sometimes an enthymematic explanation is circular, but the circularity disappears once the details are filled in.