How we change what others think, feel, believe and do
When the other person says they want something, ask why. Why do they want X? Why are they proposing action Y?
You can go up the causal chain, looking at consequences of proposals. You can also go back up the chain, looking at what led them to their current position.
Cause questions include:
In particular, if you can show how they can get what they really want by another method, you may be able to change their minds, or at least get them to accept another way.
How will you get that to work?
If you do that, what else will happen?
Why do you need to take a week? If I can show you how to do it in a day, can we go with that?
Asking why repeatedly can help you get to the real purpose of the other person's actions. This is itself useful. It may also let you challenge
Cause and effect is often not carefully considered when people decide what they want and what should be should do and what they want. It is often considered to be a straight line, with one cause leading to one effect, which then leads to a secondary effect, and so on. This simplicity of thinking is easy to challenge, though people may use irrational arguments to defend their reasons (such as 'It stands to reason').
In practice, one action can have many effects, not all of which are desirable. Cause and effect can also be circular, which be a spiral up or a spiral down (for example the way exposure leads to more fame, which leads to exposure). Even when the cause and effect as assumed are correct, a range of side-effects can appear, for example in the way spending more on a target project that makes it successful may mean diverting funds from other projects which then fail.
When the other person asks you why, then you can avoid this by making it a 'confidential' item that you are unable to discuss. Another route is to move on quickly, using urgency to gloss over any logical inaccuracies.