How would you assess what really happened without having assumptions? You will never know what really happened because our senses are limited.
Reality is our agreement on what we can call congruent perception.
Discussion
Yes this is true. For single events, the truth can always only be estimated. But for general rules, these estimations get very dense and condensate eventually to a shared idea about how the reality is.
Like probably everyone would assume, that a drop of water on a dry sponche will be sucked up.