One of my favorite quotes about learning. From this article, Taking Learning Seriously the entirety of which is worth reading. But for now here is the quote, and a visual (just because):

Learning is least useful when it is private and hidden; it is most powerful when it becomes public and communal. Learning flourishes when we take what we think we know and offer it as community property among fellow learners so that it can be tested, examined, challenged, and improved before we internalize it — Lee Shulman