How many times have we stumbled upon things that we believed were true? How many of them would we have avoided if we had stopped in order to question our knowledge and separate certainties from assumptions?
Every day we take for granted many things that surround us. When we do it in a project, life, or professional, if we are not aware of the validity of the assumptions we start from, we will also be unaware of the potential risks we are taking.
An on the road journey , planned in detail, is likely to fail if we take it for granted that our car can support it. If we were wondering if the simple fact that it has never given us a problem so far is enough to make sure it can take a long way, we would probably plan that more in-depth check that will allow us to discover the failures that will likely be ruining our journey.
What could happen if our project sponsor tells us that all the figures we need are already employees in the company and, consequently, we plan all the work based on his information without questioning it? Everything could go as planned, or it could happen that, at some point in the project, we realize that the resources don't have the skills we need.
The consequence? Probably, unplanned costs to acquire new resources and remedy the mistakes made by the previous ones, and huge delays in our schedule.
If we had identified the sponsor's statement as an assumption and not a certainty, if we had monitored it through our Assumption Log and validated, we would have already had the opportunity to intervene in time with a plan B.
English 
Italian