The discipline of philosophy has often been singled out for objections on grounds of utility. My suspicion is that modern economic claims against philosophy are merely just permutations of a timeless sense that philosophy is hard and philosophers are annoying.
Although there are probably countless passages defending philosophy against its attackers, here are a few starts at explaining why everyone needs it.
“In truth, those who practice philosophy correctly practice dying.”
τῷ ὄντι ἄρα, ἔφη, ὦ Σιμμία, οἱ ὀρθῶς φιλοσοφοῦντες ἀποθνῄσκειν μελετῶσι
Montaigne offers interpretations of this idea:
“Cicero sayeth that to Philosophize is no other thing than for a man to prepare himself to death: which is the reason that study and contemplation doth in some sort withdraw our soul from us, and severally employ it from the body, which is a kind of apprentisage and resemblance of death. Or else it is that all the wisdom and discourse of the world doth in the end resolve upon this point: to teach us not to fear to die. Truly either reason mocks us, or it only aimeth at our contentment, and in fine bends all her travel to make us live well and, as the holy Scripture sayeth, at our ease. All the opinions of the world conclude that pleasure is our end, howbeit they take diverse means unto and for it, else would men reject them at their first coming. For who would give ear unto him that for its end would establish our pain and disturbance?”
Plutarch, An Virtus Doceri Possit (“On Whether Virtue Can Be Taught) 439a
“We are deliberating and debating about virtue, whether it, or thinking, acting and living well can be taught. So we are surprised that the accomplishments of speakers, captains, musicians, architects and farmers are countless, while ‘good men’ are merely named and mentioned, like ‘Centaurs’, ‘Giants’, and Cyclopes. It is also not possible to find any achievement that is faultless in respect to virtue, or a character pure of passions or a life untouched by shame. Yet, even if nature does offer anything noble on its own, mustn’t it be obscured by much else, the way wheat is mixed with wild and impure weeds?
Men learn to play strings, to dance, to read, to farm and to ride horses. And why is that strange? They learn to put on shoes and clothes, they learn to pour wine and to cook. These things cannot be done well without learning. But the reason all these things are done—living well—that is unteachable, irrational, artless and by chance?”
Περὶ τῆς ἀρετῆς βουλευόμεθα καὶ διαποροῦμεν, εἰ διδακτόν ἐστι τὸ φρονεῖν τὸ δικαιοπραγεῖν τὸ εὖ ζῆν· εἶτα θαυμάζομεν, εἰ ῥητόρων μὲν ἔργα καὶ κυβερνητῶν καὶ ἁρμονικῶν καὶ οἰκοδόμων καὶ γεωργῶν μυρί’ ἐστίν, ἀγαθοὶ δ’ ἄνδρες ὀνομάζονται καὶ λέγονται μόνον, ὡς ἱπποκένταυροι καὶ γίγαντες καὶ κύκλωπες, ἔργον δ’ ἀμεμφὲς εἰς ἀρετὴν [καὶ ἀκέραιον] οὐκ ἔστιν εὑρεῖν οὐδὲ πάθους ἀκέραιον ἦθος οὐδ’ ἄθικτον αἰσχροῦ βίον, ἀλλ’ εἰ καί τι καλὸν ἡ φύσις αὐτομάτως ἐκφέρει, τοῦτο πολλῷ τῷ ἀλλοτρίῳ, καθάπερ ὕλῃ καρπὸς ἀγρίᾳ καὶ ἀκαθάρτῳ μιγνύμενος, ἐξαμαυροῦται; ψάλλειν μανθάνουσιν οἱ ἄνθρωποι καὶ ὀρχεῖσθαι καὶ ἀναγινώσκειν γράμματα καὶ γεωργεῖν καὶ ἱππεύειν· καὶ τί δεινόν; ὑποδεῖσθαι μανθάνουσι περιβάλλεσθαι, οἰνοχοεῖν διδάσκουσιν ὀψοποιεῖν· ταῦτ’ ἄνευ τοῦ μαθεῖν οὐκ ἔστι χρησίμως ποιεῖν, δι’ ὃ δὲ ταῦτα πάντα, τὸ εὖ βιοῦν, ἀδίδακτον καὶ ἄλογον καὶ ἄτεχνον καὶ αὐτόματον;
“We must always take care that we do not become so devoted to one branch of learning that we neglect the others, nor should we, by applying ourselves too closely to natural science neglect the study of morals or the business of everyday life.”
Semper autem cavendum est, nec, si uni iungamur arti, ut reliquas negligamus, neve naturalibus inhaerentes studiis ac contemplationibus, quae moralia sunt postponamus et rebus abducamur agendis.
-Aeneas Silvius Piccolomini, de Liberorum Educatione, chp. 94
This sentiment is echoed in David Hume’s Enquiry Concerning Human Understanding, section 1:
“Be a philosopher; but, amidst all your philosophy, be still a man.”
Of course, sometimes philosophy is just a back-up plan:
Plato Was a Bad Poet, so He Turned to Philosophy: Aelian, Varia Historia 2.30
“Plato, the son of Ariston, at first pursued poetry and used to write heroic verse. But he soon burned it all because he despised it, since he reckoned that his poetry was far inferior when compared to Homer’s. He then tried tragedy and even completed a tetralogy, and he was about to enter the competition, even to the point of giving the verses to actors. But right before the Dionysia, he went and heard Socrates; and once he was seized by that Siren, he not only withdrew from the competition, but he also gave up the writing of tragedy for good to immerse himself in philosophy.”
Πλάτων ὁ ᾿Αρίστωνος τὰ πρῶτα ἐπὶ ποιητικὴν ὥρμησε, καὶ ἡρωϊκὰ ἔγραφε μέτρα• εἶτα αὐτὰ κατέπρησεν ὑπεριδὼν αὐτῶν, ἐπεὶ τοῖς ῾Ομήρου αὐτὰ ἀντικρίνων ἑώρα κατὰ πολὺ ἡττώμενα. ἐπέθετο οὖν τραγῳδίᾳ, καὶ δὴ καὶ τετραλογίαν εἰργάσατο, καὶ ἔμελλεν ἀγωνιεῖσθαι, δοὺς ἤδη τοῖς ὑποκριταῖς τὰ ποιήματα. πρὸ τῶν Διονυσίων δὲ παρελθὼν ἤκουσε Σωκράτους, καὶ ἅπαξ αἱρεθεὶς ὑπὸ τῆς ἐκείνου σειρῆνος, τοῦ ἀγωνίσματος οὐ μόνον ἀπέστη τότε, ἀλλὰ καὶ τελέως τὸ γράφειν τραγῳδίαν ἀπέρριψε, καὶ ἀπεδύσατο ἐπὶ φιλοσοφίαν.