The quote "It is not what we do not know that gives us trouble, it is what we know that is not so" is often attributed to American humorist and newspaper columnist Josh Billings. However, variations of this quote have been used by several other individuals throughout history, and its exact origin is not entirely clear.
Josh Billings, whose real name was Henry Wheeler Shaw (1818–1885), was known for his wit and humorous observations on various subjects, and this quote reflects his clever take on knowledge and ignorance. While he is frequently credited with this saying, it's possible that similar expressions existed before his time.
Regardless of its origin, the quote conveys a valuable idea about the potential pitfalls of mistaken beliefs and the importance of critical thinking and self-awareness when navigating the complexities of knowledge and understanding.