The old saying goes that when you assume something it makes an "ass" out of "u" and "me." That's been demonstrated numerous times. The word assumption does have several definitions. The one in reference above is listed first below. I want to discuss the second definition in relation to the first.
1. a thing that is accepted as true or as certain to happen, without proof
2. the action of taking or beginning to take power or responsibility
The key term to the first definition is "without proof." If we invoke definition two, and take responsibility for defining and offering a level of proof to the assumption, then we have a powerful tool for communication and negotiation.
In a talk given by James Lara of Greystone Partners at the 2016 NBAA annual meeting, he was discussing the difficulties many of us find in developing a budget. Many times we get into struggles or face the limits of "do more with less." James stated that if you agree on the assumptions to use in developing the budget, the rest becomes straightforward. With respect to the budget, first agree what the assumptions are. How many trips or hours are needed this year by how many passengers? How many days on the road are needed? What standards do we train to and what are the crew-rest and time-off policies? If fuel cost, salaries, insurance levels, and other costs are mostly a given, then all that remains is the calculation of the total costs to deliver the transportation, safety, and service levels we have just agreed to (assume). If there is a disagreement on the numbers, refer back to the agreed-to assumption that leads to the number.
This applies to all sorts of communications and relationships. What are the assumptions we are dealing with and are we in agreement? We had this recently at work. We were discussing an issue with one of our software products. When several of us got on a call to discus it, we first had to decide whether it was a problem with the software feature not working correct or whether we didn't communicate to folks what the feature was supposed to do. Once we decided that the issue was the feature didn't do what it was supposed to do, we then set out to reconfigure the feature. And yes, to communicate with our customers better is needed, too. We avoided a lot of wasted time by agreeing what the assumption was in relation to the software before we went down the path to fix it.
This also helps in our relations with other people. With one client, we were tasked to look at their staffing. One area where the assumptions were quite different was in respect to the "free time" when the pilots were on the road. If the aircraft owner went to Barbados for a week, the plane and crew stayed down there as well. On one hand, it sounds good to have a few days in Barbados. But the pilots are not with family. They are not able to be totally free with their time in case the aircraft owner changes plans. So is this assumed to be work or time off?
If you are creating a new position or moving someone into a new position, you need to make sure they understand what the job duties and performance criteria are. Helping a client select an aircraft? Do they assume a single-engine turboprop is a safe and cost-effective alternative or are they nervous fliers who want two engines and two pilots at all times?
Too often we assume the other person has the same assumptions, goals, and reasons for being as we do. When we run into resistance, we can be taken aback to find that is not always true. Checking that your assumptions are in alignment with the other person can avoid many issues and miscommunications. Make it your responsibility to check in with the other person to at least agree on what the baseline considerations are. It's time well spent.