The Map is not the Territory

....the differences between belief and reality. The phrase was coined by Alfred Korzybski. Our perception of the world is being generated by our brain and can be considered as a 'map' of reality written in neural patterns. Reality exists outside our mind but we can construct models of this 'territory' based on what we glimpse through our senses.
(Wikipedia)

Brexit comes to my mind in terms of the differences between belief and reality ....