My father-in-law loved to do jigsaw puzzles, and would always begin by separating the pieces according to color. He worked on a large surface, so he had room to spread out, with all of the blue pieces in one pile, all of the red pieces in another pile, all of the dark pieces together, and so on. For this initial sorting, he wasn’t concerned whether a blue piece was part of the sky or part of the water, or if a dark piece was part of a tree trunk or the side of a barn. Those finer distinctions would come later as he went on to put the puzzle together.

As he worked, he would sometimes carefully examine a single puzzle piece and hold it up to the completed picture on the box, until that aha! moment where he would find its exact spot. Suddenly he could see that the bit of blue was indeed wat…