Our actions are based on our beliefs and the results of those actions are the basis for our beliefs. The difficulty we create for ourselves is that we make assumptions as to how to interpret the results we select based on our beliefs. As a result we are often operating on a flawed perspective of reality. There is a also a video
for this insight which is a component of the Effective Problem Solving Course
We make assumptions all the time. It's almost impossible to do anything without assumptions coming into play. The problem is that often our assumptions are incorrect and as a result things don't turn out the way we expect them to.
The ladder of inference was developed by Chris Argyris in 1990 as an explanation as to how we traverse from observable data to actions that we take based on our beliefs.
Beliefs are established based on the connections we make with current beliefs. And, beliefs limit the data and experience we select to pay attention to. Mostly we select what is consistent with our beliefs.
Actions are influenced by beliefs.
Real data and experience is produced by actions.
We select which data and experience to pay attention to.
We affix meaning to the data and experience we select.
We develop assumptions based on the meaning we have affixed.
We form connections between assumptions.
The is a growth and development loop which is responsible for our belief development.
This is a balancing loop where our beliefs actually get in the way of our learning development. This is a limits to growth structure.
Your mind is only able to "see" what it believes in the first place (i.e., it only sees what its mental models allows it to distinguish in reality). Critical thinking is a way of deciding the truth of things. Wikipedia
From this set of interactions it should be apparent why it is so critical to identify and test assumptions least we operate from an invalid foundation.