On Metaphysics (1850-1874)

“Metaphysics. The science to which ignorance goes to learn its knowledge, and knowledge to learn its ignorance. On which all men agree that it is the key, but no two upon how it is to be put into the lock.” (Augustus De Morgan, [letter to Dr. Whewell] 1850)

“Religion is the metaphysics of the masses […] Just as they have popular poetry, and the popular wisdom of proverbs, so they must have popular metaphysics too: for mankind absolutely needs an interpretation of life; and this, again, must be suited to popular comprehension.” (Arthur Schopenhauer, “The Horrors and Absurdities of Religion”, 1851)

“Some think to avoid the influence of metaphysical errors, by paying no attention to metaphysics; but experience shows that these men beyond all others are held in an iron vice of metaphysical theory, because by theories that they have never called in question.” (Charles S Peirce, 1867)

“Nor do I know any study which can compete with mathematics in general in furnishing matter for severe and continued thought. Metaphysical problems may be even more difficult; but then they are far less definite, and, as they rarely lead to any precise conclusion, we miss the power of checking our own operations, and of discovering whether we are thinking and reasoning or merely fancying and dreaming.” (Isaac Todhunter, “Conflict of Studies and Other Essays”, 1873)

"The history of civilization proves beyond doubt just how sterile the repeated attempts of metaphysics to guess at nature’s laws have been. Instead, there is every reason to believe that when the human intellect ignores reality and concentrates within, it can no longer explain the simplest inner workings of life’s machinery or of the world around us." (Santiago Ramón y Cajal, "Reglas y Consejos sobre Investigacíon Cientifica: Los tónicos de la voluntad", 1897)