Thesis: In the face of the same data, two rational people will make the same decision.
Implication: When two people disagree on something it is likely that there is something one knows that the other does not.
Strategy: When two people disagree, each should strive to reveal what is relevant that s/he knows and that the other does not until both know everything that the other knows.
Conclusion: Agreement should be reached if both are rational; that is, neither is acting based on self-interest, emotion, fear, etc.
Implication: When you reach an impasse with someone on an important matter, reflect on what is important that you know that the other party might not know and offer to share it. Similarly, ask the other party what s/he knows that is important that you may not know.
Caution: Politics and wildly divergent assumptions about the world and the way it works can overwhelm this practical approach. That said, it is a surprisingly useful mindset and approach to use in most day-to-day operating circumstances.