Disagreement

There are three main reasons for the insistence on disagreement.
It is first, the only safeguard against the decision-maker's becoming the prisoner of the organization. (...) The only way to break out of the prison of special pleading and preconceived notions is to make sure of argued, documented, thought-through disagreements.

Second, disagreement alone can provide alternatives to a decision. And a decision without an alternative is a desperate gambler's throw, no matter how carefully though through it might be. There is always a high possibility that the decision will prove wrong. (...)

And above all, disagreement is needed to stimulate the imagination. One does not, to be sure, need imagination to find the right solution to a problem. But then this is of value only in mathematics. In all matters of true uncertainty such as the executive deals with, (...) one needs "creative" solutions that create a new situation. And this means that one needs imagination- a new and different way of perceiving and understanding.

The Essential Drucker
Peter F. Drucker
Collins Business 2005