"Had Greek civilization never existed," wrote WH Auden, "we would never have become fully conscious." Our world was shaped by the ancient Greeks and, like it or not, for the past 600 years we have been coming to consciousness within their aesthetic legacy. At the beginning of this century, the modernists proudly rejected wholesale the pre-eminence of the Greek ideal. But a newly opened gallery at the British Museum suggests that they may have thrown the baby out with the bathwater.

It is not the familiar classical model that the new gallery celebrates, but the Hellenistic period, a later flowering of Greek art, a study of which might offer new insight into the cultural vagaries of our own age. The art of the Hellenistic period, which can be dated from the death of Alexander the Great in 323BC to the fall of Egypt in 30BC, differs distinctly from that of the earlier classical world, and in key areas foreshadows certain central themes of modern art. Here, for example, in works such as the peasant boy, The Spinario, extracting a thorn from his foot, is the beginning of portraiture as we know it - as an investigation into character and individuality. It was in the Hellenistic age, in the writings of Pliny and Douris, that the concept of art history can be said to have been invented. It is largely through their work that we know that Hellenistic artists, in contrast to their classical predecessors, were concerned primarily with the abstract forces that condition human experience - Kairos, Tyche and Eros: Chance, Fortune and Love.

Here, too, we find the first example of the supposedly modern, cynical relationship between critic, collector and artist - in Pliny's praise of that triumph of Hellenistic baroque, The Laocoon, owned by his own patron, the emperor Titus. Most importantly, in this atmosphere of unprecedented artistic consciousness was born the abiding aesthetic distinction between the ideal and the real. Classical perfection was now reserved for the Gods, while mortals, whatever their station, were defined by an increased realism.

This aesthetic revolution was brought about by the nature of the post- Alexandrine world - a vast, self-conscious, multicultural, multi-racial, increasingly mobile society reaching from Europe to India, in which the notion of the individual eclipsed that of the state. It is not difficult to find parallels with our own age. Then, as now, the visual arts offered a seemingly unprecedented choice. And, as any culturally diffuse society will always reveal hidden anxieties and tensions, these inform Hellenistic sculpture just as they do the work of today's most interesting artists.

Despite 500 years of imitative neo-classicism and a century of modernist rejection and vacuous post-modernist borrowings, the reality of Greece remains elusive, subject to the interpretations attempted by successive generations. Confronted by the British Museum's new gallery, however, we can no longer ask"does this formally enhance our art?" but should enquire instead into the very purpose of that art itself. This is not just a collection of archaeological fragments: it is an opportunity, before the millennium, to come to terms with our own cultural identity.

n British Museum: 0171-636 1555