<p>In this paper I propose a concept to describe the circular developmental trajectory of psychometrics of intelligence in the twentieth century, and I argue that this circularity explains the degenerate character of the field. Defining, measuring, and explaining intelligence formed a closed circuit of reciprocal refinement activities. I call this circular, internally guided, and non-progressive refinement process degenerate bootstrapping. Bootstrapping, especially in the initial stages of a science, is inevitable and might end up with better measuring instruments and a better theoretical foundation. In the psychometric intelligence case, the absence of truly test-independent benchmarks, over-reliance on test score correlations, and the absence of genuine theorizing prevented the field from making significant conceptual progress. The circularity is specific to psychometric intelligence research and the diagnosis of degenerate bootstrapping does not apply to neighboring fields and approaches. To describe the bootstrapping process, I will offer a conceptual history, starting with Alfred Binet and focusing on the work of American founders, namely, Lewis M. Terman and David Wechsler. Methodological and conceptual aspects of the circular modifications will be discussed with special emphasis on the definition and measurement of intelligence as well as the status of factor-analytic theories. A current brain based theory of intelligence, Parieto-Frontal Integration Theory (P-FIT) can escape this circularity to the degree that it goes beyond the conceptual confines of psychometrics.</p>