 The world we inhabit isn’t an undifferentiated bog. Everywhere there’s repetition and, importantly, we can even distinguish different types of repetition. We see one cat and then another cat. But we can also see that our cat is on top of the mat and subsequently notice that the cat from next door is on top of the fence. Repetition in the first sense requires only one thing and then another. By contrast, repetition in the second sense requires two (or more) things and then two (or more) other things. Properties are typically introduced to account for repetition in the first sense, whereas relations are typically introduced to account for repetition in the second sense. There’s cat repetition because there is more than one thing that has a certain property, the property of being a cat. There’s above-and-below repetition because there is more than one thing that bears a certain relation to something else, the relation that holds between two things when one is on top of the other.