"In speaking of Thomas Aquinas, who, it is true, had not attained at the time when Roger Bacon wrote to the commanding…"

"Do there exist many worlds, or is there but a single world? This is one of the most noble and exalted questions in th…"

"Of Albertus Magnus, the Doctor Universalis of the Dominicans, Roger Bacon writes that what is useful in his works mig…"

"If the excrement of an elephant should be smeared on skin in which lice appear and left until it dries upon the skin,…"

"The metals are all essentially identical; they differ only in form. Now, the form brings out accidental causes, which…"

"This dumb ox will fill the world with his bellowing."

"Natural science does not consist in ratifying what others have said, but in seeking the causes of phenomena."

"Aufgabe der Naturwissenschaft ist es nicht, alles, was berichtet wird, einfach hinzunehmen. Sie hat vielmehr die Ursa…"

"Allein Beobachtung gibt nämlich derartigen Dingen Gewissheit."

"Wer Dankbarkeit fordert, verdient keine."