Nomothetic literally means "proposition of the law" (latin derivation) and is used in both philosophy (see also Nomothetic and idiographic) and in psychology with differing meanings. In psychology, nomothetic measures are contrasted to ipsative or idiothetic measures, where nomothetic measures are measures that can be taken directly by an outside observer, such as weight or how many times a particular behavior occurs, and ipsative measures are self-reports such as a rank-ordered list of preferences.