Everyone thinks they have all the common sense they need. Rene Descartes:
"Good sense is mankind's most equitably divided endowment, for everyone thinks that he is so abundantly provided with it that even those with the most insatiable appetites and most difficult to please in other ways do not usually want more than they have of this."
Other people's common sense often appears to be nonsense. Thomas Cathcart and Daniel Klein:
"...you don’t need to be an epistemologist to realize that one person’s 'self-evident' is another person’s 'huh??'"
Nikki Stern wrote: "Our culture creates 'junk thought.' Susan Jacoby, author of The Age of American Unreason, attacked our intellectual laziness, which she tied to our easy validation of ideas without merit."
Sometimes people really do have good sense and expertise on top of that, but it is admirable to be humble about it. Yoshida Kenko:
"One should never make a show of having a deep knowledge of any subject. Well-bred people do not talk in a superior way even about things they have a good knowledge of. It is people who come from the country who offer opinions unasked, as though versed in all manner of accomplishments. Of course some among them do have a really enviable knowledge, and it is their air of self-conceit that is so stupid. It is a fine thing when a man who thoroughly understands a subject is unwilling to open his mouth, and only speaks when he is questioned."
It's no shame to be ignorant and curious. That's how we grow in our knowledge. Sue Halpern:
"How do people know what they know? This is always the question. The world presents itself: the sky is blue, the birds are singing. Our senses are an open window. A breeze is always blowing through. How do we know what cannot be proved? The answer is as unsatisfying as it is true: We just do. There are times when this is enough, and times when it is discomfiting. Recognition of a world that is not the familiar, material one is unsettling; it is hard enough to keep track of this world. Science, like belief, starts with wonder, and wonder starts with a question. As Bill Calvert would have told the students, answers did not dispel the wonder, they reinforced it. Answers begot questions, and questions were the libido of intelligence. How better to describe the endless pursuit of knowledge than passion?"
Rene Descartes. "Discourse on the Method of Rightly Conducting the Reason and Seeking Truth in the Field of Science." Discourse on Method and Meditations. Translated by Laurence J. Lafleur. Indianapolis: Bobbs-Merrill Educational Publishing, 1960. p 3.
Thomas Cathcart and Daniel Klein. Aristotle and an Aardvark Go to Washington: Understanding Political Doublespeak Through Philosophy and Jokes. New York: Abrams Image, 2008. p. 120.
Nikki Stern. Because I Say So: The Dangerous Appeal of Moral Authority. Bascom Hill Books, 2010. p. 12. The "junk thought" quote is cited to Susan Jacoby, The Age of American Unreason (New York: Pantheon Books, 2008), p. 211.
Yoshida Kenko (1283-1350), "Propriety," 17. "Adapted from The Tzuredzure gusa of Yoshida no Kaneyoshi translated by George Sansom. Asiatic Society of Japan Transactions, 39, 1911. A longer extract is printed in Anthology of Japanese Literature compiled and edited by Donald Keene. Grove Press New York 1955."
Sue Halpern. Four Wings and a Prayer: Caught in the Mystery of the Monarch Butterfly. London: Weidenfeld and Nicolson, 2001. p 199.