Good faith is a principle prominent in civil law countries but less so in common law countries, and which allows courts to deviate from black letter law. It provides them with flexibility to change the outcome of a deductive legal decision if they regard it as absurd. The principle of good faith thus empowers the judiciary to deviate. It can be used for an indefinite number of cases and might lead to almost all conceivable legal consequences. For instance, the judge can invalidate the contract, change the price, suspend or change a clause in the contract, or grant injunctive relief, compensation of damages, the disgorgement of profits or a removal claim. We argue that if the principle of good faith is used to develop contract law into an instrument for redistributing wealth in favor of poor parties, this can destroy the concept of contract as a social mechanism for generating mutual gains for parties, which might lead to unwanted economic consequences in terms of efficiency losses. We argue that the principle of good faith must be carefully and reluctantly used to reconstruct the fully specified contract and that well-informed judges, who understand the factual environment of a contract well should ask how fair bur self-interested parties would have allocated the risk in a pre-contractual situation. If the courts restrict the application of the good faith principle to these functions, this provides elasticity that otherwise would not exist if courts would strictly use the rules laid down in black letter law. Moreover, it saves transactions costs and is therefore in line with economic reasoning. We look at the most important Turkish cases and find that the Turkish Supreme Court following Continental European doctrines of good faith actually uses this principle to curb opportunistic behavior of parties and not to achieve redistribution from the rich to the poor by way of interfering into contract law.