Comparison comparison, putting two or more things side by side to see how they are alike and how they differ, is how we make sense of the world. Is this stick longer than that one? Is this fruit sweeter? Is this path safer? We answer by comparing. We do not need a ruler or a scale at first. We need attention and a way to hold both in mind. First, we choose what to compare and what aspect we care about. Length, weight, taste, danger—each is a dimension. Then we observe. Sometimes we can put the two things right next to each other. Sometimes we have to remember one while we look at the other. Comparison is the basis of measurement. Before we have numbers, we have "more," "less," "same." Comparison can mislead. We might compare the wrong things. We might ignore a dimension that matters. We might forget that "same in one way" does not mean "same in all ways." So learning to compare well means being clear about what we are comparing and what we are not. When we pass knowledge on, we often pass on ways of comparing—this is how we tell a good tool from a bad one, a ripe fruit from an unripe. What two things did you compare recently? What did you learn?