[Those] who have an excessive faith in their theories or in their ideas are not only poorly disposed to make discoveries, but they also make very poor observations. - Claude Bernard (1813-78) French physiologist, 1865.
The dispassionate intellect, the open mind, the unprejudiced observer, exist in an exact sense only in a sort of intellectualist folk-lore; states even approaching them cannot be reached without a moral and emotional effort most of us cannot or will not make. - Wilfred Batten Lewis Trotter (1872-1939) English surgeon.
Sherlock Holmes, although fictional, is a great proponent of observation, data, and theory - in that order.
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories instead of theories to suit facts. - Sherlock Holmes, the fictional creation of Arthur Conan Doyle (1859-1930) British physician and novelist.
George Santayana offers this definition which seems to agree with my own sentiments.
Science is nothing but developed perception, interpreted intent, common sense rounded out and minutely articulated. - George Santayana (1863-1952) U. S. philosopher and writer. The Life of Reason.
Lastly, Voltaire has this witty comment.
Common sense is not so common. - Voltaire, a French Enlightenment writer, historian, and philosopher.