This paper critically reviews some of the basic assumptions in the traditional theory of social choice, namely, the interpersonal independence and invariance of individual preferences, and the independence from irrelevant alternatives in the choice set. A new approach is proposed which would violate these assumptions but, rather, assumes the situation dependency of preferences in social decision. Experiments were done to investigate people's intuitive principles for “desirable concessions” approaching to the mutual agreement, where the situation-dependency was assumed to be taken into account. Analyzing subjects' judgements for “desirable steps” of concessions, three underlying principles were found to be mostly sufficient for describing their divergent responses:That is, they adopted either an efficiency-oriented principle, and equity-oriented principle, or a rank-position-oriented principle, each of which reflects a different philosopy for the desirability of social concession processes and group decision outcomes. Implications of these principles in both theory and practice are also discussed.