The idea of this paper is that if decision-making processes are more considered in a procedural rationality assumption, then the interplay of trust and calculative reasoning, and, at a more collective level, the interplay of contracts and social networks may be clarified. We use Lindeberg's framing theory to define enlightened self-interest as the rationality of contractual relationships. Cooperation is then explained by the willingness to pursue the relationship which, from the background, decreases the salience of the gain frame. This willingness is supported by a process of mutual relational signaling. When temptations of opportunism are strong, cooperation needs to be embedded, first in a formal contract and the, if stakes are too high, in a social network. In this framework, we show that the acceptance of contractual incomplete by the parties is a positive signal which favors cooperation.