 In human and animal psychology since Darwin there have been a number of periods when the innate/acquired distinction was the subject of heated scientific controversy. This section reviews some of these debates. It provides a sense of how different scientists have conceptualized instinct or innateness, the kinds of evidence marshalled to support nativist hypotheses, and some of the recurring objections that nativist proposals have encountered. In scientific psychology the words “innate” and “instinctive” have been used to refer to the same cluster of properties, “instinct” being a now somewhat antiquated term for an innate psychological trait. Hence, in this section we take older debates over instinct to be about the same set of issues as more recent debates over innateness.