In business, it's not unusual be confronted with a decision that somebody else has made but which you would like to change. Your first impulse is probably to present evidence that proves the current decision to be wrong.

That, however, is a huge mistake. People tend make decisions emotionally and only then evaluate the evidence. Once they've made a decision, people tend to either disbelieve contrary evidence or mentally manipulate the evidence so that it supports their decision.

In other words, when people are wrong about something, the more evidence you present that they're are wrong, the less likely they are to change their minds.

For example, when confronted with evidence that climate change is happening, deniers either dismiss the evidence as part of a "liberal conspiracy" or hijack the evidence to confirm their point. (E.g. "it's colder this year than last year, therefore it's all nonsense.")

Similarly, Macintosh fans and Windows fans alike have mountains of evidence as to why their preferred platform is "better." Despite decades of debate, I doubt if more than a handful of people have actually changed camps.

Business decisions aren't usually as set in mental concrete than the examples above, but the same psychological pressure to rearrange evidence to fit the decision plays a very real role.

If evidence doesn't work, how do you change somebody's mind? Here's the process, followed by an example:

1. Agree with them.

With human beings, pressure always creates resistance, so your first step is always to get on the same side of the table. This doesn't mean that you abandon your position, but it does mean that must you express support for whatever truths you can find in the other person's decisions and opinions.

2. Reframe the problem.

Decisions and opinions always emerge from a certain way of looking at the problem. When you change the problem's definition, you open up the possibility of escaping from the standard back-and-forth. The other person no longer needs to defend his or her viewpoint, because you've changed the "view."

3. Introduce a new solution.

Once you've reframed the problem and the other person has accepted the reframe, you can suggest a solution that solves the newly-defined problem. At this point, you can introduce evidence, not that the other person is wrong, but that--given the problem's new definition--a different decision might be right.

4. Provide a way to "save face."

People often cling to decisions and opinions simply because they're afraid they'll look stupid if they "back down." Therefore, when you want a person to change his or her mind, you must offer them a dignified way to do so.

For example, suppose your customer announces that she's buying from another vendor. You naturally want her to change her mind and buy from you instead. The conversation might go two ways:

Wrong:

Customer: "We've decided to go with XYZ."

You: "Here's an analyst report presenting evidence that our product is higher quality." (Evidence.)

Customer: "Analysts only say what they're paid to say." (Disqualifies evidence.)

You: "But their products don't last as long."

Customer: "They have plenty of customers." (Selecting supporting evidence.)

You: "You've made the wrong decision."

Customer: "Maybe so, but it's MY decision."

Right:

Customer: "We've decided to go with XYZ."

You: "I'm sorry to hear that. For my own understanding, could you explain why you're making that decision?"

Customer: "Their lower price fits into our budget."

You: "XYZ has a very good product and their price is indeed lower that ours. If I were in your shoes, I'd be looking very closely at their offering." (Agreement.)

Customer (a bit confused): "Oh. You think it's a good decision, then?"

You: "Yes, and I was also wondering if you considered the issue of total cost of ownership." (Reframe.)

Customer: "No, because I'm more concerned with this quarter's budget."

You: "I understand. The reason I ask is that I can show you independent evidence of how, in the long term, you'll save money with our product." (Solution.)

Customer: "But what about this quarter?"

You: "If we could spread the payment out over several quarters, would you be willing to reconsider?" (Face saving.)

Customer: "Maybe. Let's see what you've got."