We cannot observe attitudes with the same exactitude that scientists employ when examining molecules under electron microscopes. We lack the attitudinal equivalent to the human genome, the long strand of DNA that contains our 23 critical chromosome pairs. Instead, we infer attitudes from what people do or say, and what they report on carefully constructed survey instruments. This does not make attitudes any less real than chemicals on the Periodic Table, the 30,000 human genes, rocks, plants, or any other material that scientists scrutinize. It simply makes our job of uncovering their basic content more challenging and perhaps more subject to human fallibility.