720 THE JOURNAL OF PHILOSOPHY many human cognitive abilities. 4 Nativist claims have been made about many traits, such as: general mental ability (as measured by IQ), personality traits, sexual preferences, political preferences, moral attitudes, obesity, and so on. For each of these traits, some authors have argued they are innate, and some authors have argued they are not. We can call these the Nativist Debates. In order for the Nativist Debates to make sense, both nativists and anti-nativists must assume that the notion of innateness (from now on, simply, innateness) is coherent and theoretically useful. 5 But, in the light of what we currently know about the development and evolu tion of biological and psychological traits, it is not clear whether this is the case. 6 In particular, it is not clear whether there is a (single) theoretically useful property to which innateness can refer. Various interesting accounts of innateness have been given, some of which will be analyzed below. Each of these accounts argues that the notion refers to a specific property of biological and psychological traits. The chosen property varies from account to account. Usually, this property relates to the genetic origins of a trait, or to its develop mental robustness, or to lack of learning in the developmental pro cess. All these accounts seem to capture some particular aspect of innateness, but no account seems to be entirely satisfactory. This sug gests that perhaps innateness conflates different properties, proper ties that, according to our current best theories, need to be kept distinct. I shall call this the Clutter Hypothesis. According to this hy pothesis, innateness is like Newton's notion of mass. As a result of Einstein's theory of Special Relativity, we now believe that Newton's mass conflates relativistic mass and rest mass. The Clutter Hypothesis says that innateness conflates different properties of biological and psychological traits just like Newton's mass conflates relativistic mass and rest mass. 7