Igor - great! I hoped this would have that effect for some students. There is a _lot_ more one can say about this. For example, in [Matthew Doty's puzzles MD1 - MD3](https://forum.azimuthproject.org/discussion/comment/16627/#Comment_16627) we learn that the logical operations "and" and "or" can be described as right and left adjoints. This is just the beginning of a long and wonderful story. But in Lecture 9 I moved straight on to considering how functions between sets fit into this story.