Why thinking is the hardest part of our brain?
Common sense: “Those plain, self-evident truths or conventional wisdom that one needed no sophistication to grasp and no proof to accept precisely because they accorded so well with the basic (common sense) intellectual capacities and experiences of the whole social body" Rosenfeld, Sophia (2014). Common sense : a political history. [S.l.]: Harvard Univ Press. p. 23. ISBN 9780674284166.
"Common sense" is the ability with which animals (including humans) process sense-perceptions, memories and imagination (phronein) in order to reach many types of basic judgments. Aristotle
So, it sounds like an animal thing and shouldn't be that difficult to access.
I disagree it's easy to think its really hard to use common sense since we live in a world of differences
The word thinking in my post meant common senses and out of the box. It's not easy.
Common sense does not exist for there is no such thing as common in a world where no 2 people are perfectly alike therefore to assume there is a common knowledge base seems flawed to me