Objections to naturalized epistemology have targeted features of the general project as well as characteristics of specific versions. Some objectors suggest that natural scientific knowledge cannot be circularly grounded by the knowledge obtained through cognitive science, which is itself a natural science. This objection from circularity has been aimed specifically at strict replacement naturalism. There are similar challenges to substance naturalism that maintain that the substance naturalists' thesis that all facts of knowledge are natural facts is not only circular but fails to accommodate certain facts. Several other objectors have found fault in the inability of naturalized methods to adequately address questions about what value forms of potential knowledge have or lack.