  Descartes explicitly responds to the charge of circularity in the manner just described. Over the years, scholars have debated whether this response is adequate. Some scholars have constructed other responses on Descartes' behalf or have found such responses embedded in his text at various locations. One type of response appeals to a distinction between the natural light and clear and distinct perception, and seeks to vindicate the natural light without appeal to God (Jacquette 1996). Another response suggests that, in the end, Descartes was not aiming at metaphysical certainty concerning a mind-independent world but was merely seeking an internally coherent set of beliefs (Frankfurt 1965). A related response suggests that Descartes was after mere psychological certainty (Loeb 1992). The interested reader can follow up this question by turning to the literature here cited (as also Carriero 2008, Doney 1987, and Hatfield 2006).