ἔχει γὰρ ὧδε. θεῶν οὐδεὶς φιλοσοφεῖ οὐδ᾽ ἐπιθυμεῖ σοφὸς γενέσθαι· ἔστι γάρ· οὐδ᾽ εἴ τις ἄλλος σοφός, οὐ φιλοσοφεῖ. οὐδ᾽ αὖ οἱ ἀμαθεῖς φιλοσοφοῦσιν οὐδ᾽ ἐπιθυμοῦσι σοφοὶ γενέσθαι· αὐτὸ γὰρ τοῦτό ἐστι χαλεπὸν ἀμαθία, τὸ μὴ ὄντα καλὸν κἀγαθὸν μηδὲ φρόνιμον δοκεῖν αὑτῷ εἶναι ἱκανόν· οὔκουν ἐπιθυμεῖ ὁ μὴ οἰόμενος ἐνδεὴς εἶναι οὗ ἂν μὴ οἴηται εἰδεῖσθαι.
The truth is this: none of the gods loves wisdom [φιλοσοφεῖν] or desires to become wise [σοφός]; for they are wise already. Nor does anyone else who is wise love wisdom. Neither do the ignorant love wisdom, or desire to become wise: For this is the harshest thing [χαλεπὸν] about ignorance, that those who are neither good [ἀγαθός] nor beautiful [καλός] nor sensible [φρόνιμος] think that they are good enough: No one desires what they are lacking when they do not think themselves lacking.
Plato, Symposium, 203E-204A, Lysis, Symposium, Gorgias, translated by W.R.M. Lamb, Loeb Classical Library, Harvard University Press, 1925, 1991, pp. 182-183, translation modified.
The Master said, "To know when you know,
and when you do not know;
that is wisdom."
Confucius, Analects II:17, translation after James Legge , Arthur Waley , D.C. Lau , and Joanna C. Lee 
At the simplest level, only people who know they do not know everything will be curious enough to find things out.
Virginia Postrel, The Future and Its Enemies, p.88 [The Free Press, 1998]
Οὐκοῦν ἐπισκοπῶμεν αὖ τοῦτο, ὦ Εὐθυφρον, εἰ καλῶς λέγεται, ἢ ἐῶμεν καὶ οὕτω ἡμῶν τε αὐτῶν ἀποδεχώμεθα καὶ τῶν ἄλλων, ἐὰν μόνον φῇ τίς τι ἔχειν οὕτω, ξυγχωροῦντες ἔχειν; ἢ σκεπτέον, τί λέγει ὁ λέγων;
Then let us again examine that, Euthyphro, if it is a sound statement [εἰ καλῶς λέγεται -- if said well, καλῶς], or do we let it pass, and if one of us, or someone else, merely says that something is so, do we accept that it is so? Or should we examine [ἢ σκεπτέον] what the speaker means [τί λέγει ὁ λέγων -- what the speaker says]?
Plato, Euthyphro 9e, G.M.A. Grube translation, Plato, Five Dialogues, Euthyphro, Apology, Crito, Meno, Phaedo, Hackett Publishing Company, 1981; Greek text, Plato, translated by Harold North Fowler, Euthyphro, Apology, Crito, Phaedo, Phaedrus, Loeb Classical Libarary, Harvard University Press, 1914, pp.34-35; translations modified.
The curious task of economics is to demonstrate to men how little they really know about what they imagine they can design.
F.A. Hayek, The Fatal Conceit, The Errors of Socialism, p.78 [University of Chicago Press, 1988, 1991; cf. Socratic Ignorance]
Nor need we fear that this [Sceptical] philosophy, while it endeavours to limit our enquiries to common life, should ever undermine the reasonings of common life, and carry its doubts so far as to destroy all action, as well as speculation. Nature will always maintain her rights, and prevail in the end over any abstract reasoning whatsoever. Though we should conclude, for instance, as in the foregoing section, that, in all reasonings from experience, there is a step taken by the mind which is not supported by any argument or process of the understanding; there is no danger that these reasonings, on which almost all knowledge depends, will ever be affected by such a discovery.
David Hume, An Enquiry Concerning Human Understanding, Section V, Part I, p. 34 [L.A. Shelby-Bigge, editor, Oxford University Press, 1902, 1972, p. 41]
Confucius said, "Those born wise, are the highest. Next come those who become wise by learning. Next again come those who learn with difficulty. They who do not learn even with difficulty, those people are the lowest."
Confucius, Analects XVI:9, translation after James Legge , Arthur Waley , and D.C. Lau 
E perché e' sono di tre generazioni cervelli -- l'uno intende da sé, l'altro discerne quello che altri intende, el terzo non intende né sé né altri -- quel primo è eccellentissimo, el secondo eccellente, el terzo inutile...
Minds are of three kinds: one is capable of thinking for itself; another is able to understand the thinking of others; and a third can neither think for itself nor understand the thinking of others. The first is of the highest excellence, the second is excellent, and the third is worthless.
Niccolò Machiavelli, The Prince [Daniel Donno translation, Bantam, 1981, p. 80], Italian text, Il Principe, Nuova edizione a cura di Giorgio Inglese [Giulio Einaudi editore s.p.a., Torino, 2013 e 2014, pp.166-167]