Could making the wrong assumption be the root cause of all that's wrong in the world? Well, not quite but it's probably up there near the top. Human beings are a rather insecure bunch and they like to have some certainty in life. If the facts are unknown they tend to make assumptions, which if left unchallenged and repeated often enough, inevitably become "facts", whether or not they are true.
In science, facts are observations that have been confirmed to the point that there is a very high probability (P) that they are true under specific circumstances, and an assumption (hypothesis) is a proposed explanation of one or more facts. Incidentally, by definition, this would mean that recently popular "alternative facts" have a high probability (1-P) of being false! Whether they annihilate each other on contact, like matter and antimatter, is an interesting thought.
In business, this can be particularly relevant for process improvement projects, when making analysis and searching for root causes. Using incorrect assumptions can lead to incorrect conclusions and undesirable outcomes. So the next time that you are listing assumptions, make sure that the facts that they are based on have a high probability of being true and are not accidentally of the alternative kind.