This paper discusses the nature-nurture controversy concerning the origins of mental abilities. Specifically, the author looks at the viewpoint of Arthur Jensen and critically examines his work. This paper presents an overview of Jensen's position followed by a discussion of shortcomings in his methodology and research techniques. The author severely criticizes Jensen's failure to define terms to reduce ambiguity. The paper then critically describes Jensen's reliance on present intelligence testing methods. The manner in which Jensen uses the term, "race", is explored. His use of the concept "race and intelligence" is also discussed. The author concludes that Jensen is advocating "the genetic fallacy", and that those with a racist philosophy can use the Jensen argument to justify their position. The writer further concludes that Jensen has been generally unscientific and irresponsible in formulating his assumptions. (Author/BW)