Art was traditionally supposed to represent things – a person; a place; even a defined feeling. One associated clearly with the expression on the faces of the artwork's subjects; or expressed itself through the subject matter. Religious devotion for the Creation of Adam; mystic, almost gnomic, versions of love or chastity in the Mona Lisa. The way in which these subjects were painted directed exactly a viewer's response to each work – this, the artist seemed to be saying, is the way you should feel. Modern art, by contrast, delved into then-unpalatable ideas about the fluidity of human emotion, of experience; the idea that one viewer's love may well be the next man's hatred. As a result, modern art was (naturally) exceedingly revolutionary, and vilified and revered in about equal parts. Proponents of the old styles recoiled in horror at the faces of these inchoate images, works of modern art whose subject wasn't even there, let alone immediately recognisable; while the bright young things of the new movement watched in awe as masters like Edvard Munch and Wasily Kandinsky somehow translated the pure matter of human experience onto canvas. Modern art, now, is accepted to the point of tedium. Like what was then the old guard, the shapes and forms of modern art are everywhere – on posters, in adverts, even in the decorative schemes found on bathroom tiles, wallpaper and rugs. We've become inured to its immediacy, its freshness and its almost prescient ability to morph before us, into an embodiment of whatever emotion is deepest in our own breast. Kandinsky's circles hang on the walls of every student room between here and France, while the Tate Modern shows us sculptures and huge canvases by the same, ever-repeated roster of Big Names. Is the day of modern art done, then? Has modern art had her time in the sun, soon to be eclipsed by something else, something other that, in its turn, will become the new modern art – shocking, even, to Damien Hirst? No. Because when Edvard Munch first painted the soul of madness, he created something, a "modern art", that would last forever – would go on forever, endlessly reinventing itself. Modern art is the art of the soul, of the mind, the emotion and the heart. Like people, modern art is ceaselessly changing, endlessly reinventing itself and the way it sees or shows the world: unlike people, modern art can't lie. It's only colours and shapes, arranged before us. And we, who look at it, see in its swirls, its geometric arrangements of colour and line, a truth looking back at us that we can only hide from each other –never from ourselves. Modern art is the truth, on canvas, presented to each and every person who looks at it. For that reason alone, modern art, the art of feeling, can never grow old.