Roger Bacon — "Theories are of no use if they cannot be tested by experiment."

"The study of perspective is a most noble science, and of great utility for all other sciences."

"For without experiment nothing can be sufficiently known. Therefore, he who wishes to be certain of the truths of things must have recourse to experiment."

"There are four chief obstacles to grasping truth: frail authority, custom, the opinion of the unlearned crowd, and the concealment of ignorance by ostentation."

"The strongest arguments prove nothing so long as the conclusions are not verified by experience."

"The present generation is so corrupt that it despises the truth, and loves falsehood."