ABSTRACT
It is a truism that we all must lump entities into equivalence classes if we are to make any sense of the world around us. It has also generally been acknowledged that there is a potentially infinite number of ways in which we could treat a class of things as equivalent. However, an important issue that has not yet received ample attention is a systematic consideration of the levels at which our conceptual representations might originate. By the time we become adults, we routinely think about classes of things that seem to encompass far more complex relations than any kind of perceptual similarity alone. Tools, vehicles, and living kinds are universal examples, as are classes of intangible things such as odd numbers, puns, or riddles. No one doubts that we are readily able to think about these classes of things, or that we use them in many kinds of everyday reasoning. However, there remains an enormous debate over how our knowledge of such classes emerges in development, and how this knowledge is neurally instantiated.
