I’m a scientist.
I don’t have a degree from Stanford or Carnegie Mellon… But I’m a scientist.
I hypothesize, test and prove.
If the result doesn’t meet my supposition, I accept that and move on.
Science required known, provable facts. Or in computer science, constants.
To prove, you need to test. To test, you need constants. You need to know with 100% certainty that the factors in your experiment are known and 100% objectively provable.
Obama isn’t an American, while a supposition, cannot be proven as fact. There are records showing otherwise.
That men are pigs, while an okay assumption, does not rely on provable facts. Any proof relies on subjective experience.
That WordPress is the best CMS on the planet? While it may control ~20% of the web, assumes that 20% thinks its the right choice and avoids supporting evidence toward other CMSes.
I can get more explicit about suppositions assumed as fact, but you get the idea.
Work with what you know. Make assumptions but allow yourself to be wrong. Data is the only thing that matters.