On Observation (-1699)

"While those whom devotion to abstract discussions has rendered unobservant of the facts are too ready to dogmatize on the basis of a few observations." (Aristotle, "De Caelo" ["On the Heavens"], cca. 350 BC)

"What we know is not capable of being otherwise; of things capable of being otherwise we do not know, when they have passed outsideour observation, whether they exist or not. Therefore the object of knowledge is of necessity. Therefore it is eternal; for things that are of necessity in the unqualified sense are all eternal; and things that are eternal are ungenerated and imperishable" (Aristotle, "Nicomachean Ethics", cca. 340 BC) 

"Nothing has such power to broaden the mind as the ability to investigate systematically and truly all that comes under thy observation in life." (Marcus Aurelius, Meditations, cca. 121–180)

"[…] it is not necessary that these hypotheses should be true, or even probably; but it is enough if they provide a calculus which fits the observations […]" (Andrew Osiander, "On the Revolutions of the Heavenly Spheres", 1543)

"Man, as the minister and interpreter of nature, dies and understands as much as his observations on the order of nature, either with regard to things or the mind permit him, and neither knows or is capable of more." (Francis Bacon, "Novum Organum", 1620)

"The science of Nature [...] should return to the plainness and soundness of observations."(Robert Hooke, "Micrographia", 1665)