Fisher and Ury are renowned for their work in negotiation theory, particularly through their influential book, "Getting to Yes." They emphasize the importance of principled negotiation, which focuses on mutual interests rather than positions. This approach encourages collaboration and aims for win-win outcomes. Their method involves four key principles: separating people from the problem, focusing on interests instead of positions, generating options for mutual gain, and insisting on objective criteria. By applying these principles, negotiators can achieve more effective and amicable resolutions in various contexts, from business deals to personal disputes.