"To read the Latin and Greek authors in their original is a sublime luxury," Thomas Jefferson wrote to Joseph Priestley in the winter of 1800. "I thank on my knees him who directed my early education for having in my possession this rich source of delight." Had Jefferson known it, he would have been dismayed to think that the dominance of classical studies was already fading as he wrote, and with it, not just intellectual luxury, but a significant factor in the western world's cultural unity. No one seriously believes that it would now be a good thing to return to a classics-based education, and the "Latin wars" of a generation ago seem well over. But, in fact, the absence of classical studies from contemporary education is a bad thing, and it is time to argue that they should be restored to a more salient place in the curriculum. The reasons are many and good.
The first is a very familiar one. In the "Latin wars", the defenders of classics routinely argued that the study of classical languages is a fine intellectual discipline, which simultaneously gives students a grasp of grammar, of style and of the roots of their own language. They were right, and a comparison of the prose of writers educated in England before and after the 1960s is a remarkable testimony to that fact. This has nothing to do with language purism - for languages constantly change, and colloquial idioms thrive and become orthodox - but it has everything to do with a respect for logic, clarity, nuance and the possession of instincts about meanings.
The second reason is more general. Western culture is so deeply imbued with its classical origins that a proper appreciation of it is impossible without some knowledge of these origins. Consider a visitor to the National Gallery in London, the walls of which crawl with allusion to ancient history and mythology, not simply as direct representations of these, but as psychological studies, as conveyors of symbolic meaning, and as a commentary on the human condition. To be ignorant of this wealth of legend and event, and to be unable to see what it means and intends, is therefore to be blind. One does not have to wrestle with gerunds and aorists to recognise Aphrodite in a painting, but to have read some of the source material, in the original tongues, for these depictions is to render one's grasp of them absolute and natural, because it becomes part of one's constitution.
There is practically no area of thought, whether in art, history, philosophy, science, politics or literature, which does not owe a great deal to ancient Greece and Rome. Without a grounding in classical culture, engagement in these fields is like doing arithmetic without knowing how to count. Moreover, as almost all the later intellectual history of the west is itself woven out of the classical legacy, a proper understanding of the thought and writing of every age before our own requires that knowledge, too. To read Spenser, Milton, Dr Johnson or Matthew Arnold without knowing what they took for granted in the way of classical knowledge is simply not to understand them fully.
This point leads to the third - the resource offered by the classics is immense, and perhaps indispensable. Their literature and philosophy shapes our mentality in a million ways - not always to our benefit: which is a good reason to be alert to its influence. Think, for example, of the assumptions underlying the concept of "aristocracy", which means "rule by the best". Think of the crushing weight of class divisions, social injustice, lost opportunities and wasted lives which, century after century, resulted from the arrogation of aristocratic privileges by a few at the expense of the many, especially when they were claimed as a hereditary right. In Aristotle's view, aristocracy meant something closer to what we now describe as meritocracy. Indeed, every form of social arrangement was canvassed and debated by the ancients, who gave them their modern names as well as content. Thinking about them now in ignorance of what lies behind them is like reinventing the wheel as a triangle.
In a yet more general way, classical culture at its best offers lessons and models of peculiarly high value. As with every age and society, there is moral dross and vileness in both the Greek and the Roman worlds, too - slavery, the oppressed status of women, lavish cruelty (especially in Rome) and decadence. But the sensibility of classical Athens and republican Rome at their best is the finest there has ever been. In Greece, the appreciation of beauty, the respect paid to reason and the life of reason, the freedom of thought and feeling, the absence of mysticism and false sentimentality, the humanism, pluralism and sanity of outlook that are so distinctive of the cultivated classical mind, are models for people who see, with Aristotle, that the aim of life is to live nobly and richly in spirit.
In Rome, in its republican period, something a little more Spartan than Athenian was admired, its virtues ("vir" is Latin for "man") being the supposedly manly ones of courage, endurance, honesty, loyalty and resolve. There is a contrast here between civic and warrior values, but it is obvious enough that, whereas one would wish the former to prevail, there are times when the latter are required: for a society in wartime; for an individual at moments of crisis, grief and struggle.
It is no good merely being told these things. To discover them for oneself, in reading the great works of classical literature, is an exhilarating and moving experience that renders one's grasp of them genuine. One can leave aside the fact that ancient Greek is a language of such breathtaking beauty and suppleness, and such expressive power, that to read it is a kind of sensual pleasure; and point only to the indelible impression its literature leaves. One can ignore the majesty and logic of Latin, and point only to the striking contemporary relevance of Cicero's arguments, or to the deeply personal effect that Seneca and Horace can have. To appreciate these things requires entering the medium of the ancient languages themselves. It is an unlucky chance that so few now do so. It is time to bring them back, and place them close to the centre of liberal education.
I spent much of my childhood in ancient Rome, with Livy next to Dickens on my bedroom bookshelves, and Virgil next to Buchan. This was a matter of luck, because it happened at the cusp of when our culture began to lose its roots. For my contemporaries and elders, it is hard to know what it is like to have a perspective on the world that does not include Mucius Scaevola and Horatius, Nisus and Euryalus, Proteus changing form on the beach with his companion sea-creatures scattered about him - and with Ovid's metamorphoses and delicious loves to boot. ("How apt was her breast for caressing!" I still hear him sigh, in reporting a dalliance; "may the gods bring me many such afternoons as this.") I feel as grateful as Thomas Jefferson about having had this opportunity, and wish that everyone else had it, too. If it could be recovered to a sensible degree, it could scarcely fail to help enlarge and civilise the public mind, not as a recreation for the few, but once again as part of the shared culture of all.
A C Grayling's The Meaning of Things: applying philosophy to life is published next month by Weidenfeld & Nicolson (£12.99)