As I write the day is becoming cloudy, but earlier it was a bright, warm, late-summer day with sunshine, blue sky and scudding clouds. I grabbed my bike and rode by the River Tay, following a good asphalted track from Monifieth to Broughty Ferry and back, stopping frequently to look at things of interest, like the recently created wildflower meadow, with its splendid cornflowers, or the great gathering of swans at the outflow of the Dighty Burn. These birds are often to be found there, along with geese, duck and curlew, as well as numerous small waders.

The outflow of this burn which meanders through Dundee from West to East, must be polluted with a variety of a harmful substances, but it also carries of variety of green river plants and small animals to the waiting swans who feed methodically. Some varieties of Corvids, rooks, jackdaws and hoodies, have learned that a swan who has just picked up a tasty morsel, will if hassled by a couple of crows, drop the morsel to drive them off, whereat a third bird will catch the food. I wouldn’t argue with a swan in a bad temper, but the crows are unimpressed.

Today I was lucky to see one of my favourite sights, a swan in flight. They seem so heavy and short-winged that one imagines them as poor fliers but in fact they can travel huge distances. These are mute swans, the commonest species in the UK although I have seem immigrant whooper swans on this river. As I watched one of the swans fly off across the river, a woman standing near me said, “Ah, they’re so beautiful!”

“So they are,” I said, and we stood companionably watching until it was only a speck in the sunlight.

Why do I find it beautiful?  I might reckon that someone who didn’t find the drawings of Rembrandt beautiful was entitled to his opinion, but someone who didn’t think swans beautiful I would regard as odd. I don’t think anyone taught me that swans are beautiful, or that there is any evolutionary advantage in swan appreciation, as there might be in my appreciation of a beautiful woman.

So what is it, my sense of beauty?

Some have interpreted it as merely a transmutation of sexual desire, a love of masculine and feminine shapes, which takes on a life of its own, and develops its own criteria of form. Like many reductive explanations this seems to me to magic a molehill of truth into a mountain.

Others suggest that it is an appreciation of complex wholes whose parts fit perfectly together, providing us with a sense that the events of our lives might be similarly ordered and meaningful. There may be something of that in my love of Bach fugues or Gothic cathedrals.

Others again speculate that our sense of beauty rests on our biophilia, our natural love of the natural world, a love which grows out of our evolution and is directed towards the world to which we are fitted. I am sympathetic to this notion, as my love for the natural world is a powerful motive in my life. Still, I think that if this theory were true, many more people would find spiders, lobsters and catfish beautiful, than seems to be the case.

Plato’s theory was that we have kept a dim memory of the world of true form from which we have fallen to be encased in matter. We respond to beauty as it points towards the loveliness from which we are presently exiled. In effect, we could dispense with Plato’s story and say that he saw beauty as directing us towards a reality that transcends our material existence. It reminds us that we don’t wholly belong to this existence or love it with a whole heart, but are made for something better that we might glimpse in the courts of the Alhambra, or the skill of an Americam gymnast, or the flight of a swan.