Normative judgments and their criteria are generally excluded as subjects of science on account of the dualism of facts and values. Meta-ethical naturalism, which attempts to present criteria for values in terms of facts, is therefore regarded as a fallacy. However, as normative judgments are produced through the workings of the mind of each individual, we may find some clues for examining the foundations or criteria of our normative judgments by analyzing the process of the working of our minds by scientific methods and thereby discovering its basic rules. This means that ethical problems can be approached and solved in the field of human science.<br> Indeed, we can find some useful scientific knowledge related to meta-ethical problems. For example, it has been demonstrated in some studies of cognitive psychology that judgments on moral values are decided by intuition, which is an emotional reaction, rather than by rational thinking. And according to recent research in evolutionary psychology, emotions function in order to gain benefits for each person in their reciprocal relationships with others. These scientific studies suggest that the ultimate foundation of normative judgments is in human intuition as an emotional reaction and the ultimate criterion of “good/bad” or “right/wrong” is whether it is beneficial to the individual in his/her reciprocal relationships with others. While there remains much scope for further verification, these studies suggest that it is possible to examine meta-ethical problems by scientific methods and support meta-ethical naturalism, which presents the foundations and criteria for normative values through factual statements.