“Since it most profits that the truly wise
Should seem not wise at all.”

Life of Marcus Cato
Bartlett's Familiar Quotations, 10th ed. (1919)

Birds (414 BC)
Context: Epops: The wise can often profit by the lessons of a foe, for caution is the mother of safety. It is just such a thing as one will not learn from a friend and which an enemy compels you to know. To begin with, it's the foe and not the friend that taught cities to build high walls, to equip long vessels of war; and it's this knowledge that protects our children, our slaves and our wealth.
Leader of the Chorus [leader]: Well then, I agree, let us first hear them, for that is best; one can even learn something in an enemy's school.
(tr. O'Neill 1938, Perseus http://www.perseus.tufts.edu/hopper/text.jsp?doc=Aristoph.+Birds+375)

introduction to De Curvis Elasticis, Additamentum I to his Methodus Inveniendi Lineas Curvas Maximi Minimive Proprietate Gaudentes 1744; translated on pg10-11, "Leonhard Euler's Elastic Curves" https://www.dropbox.com/s/o09w82abgtftpfr/1933-oldfather.pdf, Oldfather et al 1933
Context: All the greatest mathematicians have long since recognized that the method presented in this book is not only extremely useful in analysis, but that it also contributes greatly to the solution of physical problems. For since the fabric of the universe is most perfect, and is the work of a most wise Creator, nothing whatsoever takes place in the universe in which some relation of maximum and minimum does not appear. Wherefore there is absolutely no doubt that every effect in the universe can be explained as satisfactorily from final causes, by the aid of the method of maxima and minima, as it can from the effective causes themselves. Now there exist on every hand such notable instances of this fact, that, in order to prove its truth, we have no need at all of a number of examples; nay rather one's task should be this, namely, in any field of Natural Science whatsoever to study that quantity which takes on a maximum or a minimum value, an occupation that seems to belong to philosophy rather than to mathematics. Since, therefore, two methods of studying effects in Nature lie open to us, one by means of effective causes, which is commonly called the direct method, the other by means of final causes, the mathematician uses each with equal success. Of course, when the effective causes are too obscure, but the final causes are more readily ascertained, the problem is commonly solved by the indirect method; on the contrary, however, the direct method is employed whenever it is possible to determine the effect from the effective causes. But one ought to make a special effort to see that both ways of approach to the solution of the problem be laid open; for thus not only is one solution greatly strengthened by the other, but, more than that, from the agreement between the two solutions we secure the very highest satisfaction.

Life Without Principle (1863)
Context: The title wise is, for the most part, falsely applied. How can one be a wise man, if he does not know any better how to live than other men? — if he is only more cunning and intellectually subtle?

Source: The Foundation series (1951–1993), Second Foundation (1953), Chapter 8 “Seldon’s Plan”

Source: The Theogony (c. 700 BC), line 120.

24. 155; translation by A. Robert Caponigri
Oration on the Dignity of Man (1496)

Variant: simple things are the most valuable and only wise people appreciate them".
Source: The Alchemist

Source: Antony and Cleopatra