H as there ever been a more theatrical artist than Rembrandt? Even when he paints himself, he paints a man playing a part, trying on an identity to see if it fits. With each new role tried out in the mirror - a biblical king or the blind poet Homer or, closer to home, a well-known Dutch painter with palette in hand - he seems less certain of who he himself actually is.

Taken together, Rembrandt's self-portraits are a visual embodiment of Montaigne's remarks on the fluid nature of consciousness: “There is no constant existence … every human nature is always in the middle between born and dying, revealing nothing of itself but an obscure appearance and shadow … and if perhaps you try to fix your thought to catch its essence, it would be like going to grasp water.”

Nearly all of Rembrandt's known self-portraits are now in public collections, so it is an event when one comes up for sale. Self-portrait of the artist, half-length, wearing a ruff and a black hat is a striking and relatively recent rediscovery. Painted in the last months of 1632, following the artist's period of activity painting portraits of associates of the court of the Dutch Stadholder in The Hague, and when he was planning to leave his native Leiden, it is a freshly painted and intimate self-image in which, as so often in Rembrandt's work, role-playing and reality are subtly at odds. On this occasion we see him dressed up in the sober finery of the Dutch merchant class. Perhaps he did so in order to advertise his propriety and solidity to his future clientele in Amsterdam, where he was setting up a studio in the house of Hendrick Uylenburch.

Or perhaps he was trying to impress his sweetheart and future wife, Saskia, in which case the picture may have been done as a keepsake for her: a hand-painted Valentine on a panel of best Baltic oak. Rembrandt's precise reason for painting it is unknown. What remains most striking about it is the variance between the clothes and the man.

He plays the part of a wealthy Dutch burgher but he can only ever be Rembrandt, and being Rembrandt is no simple matter. There is a wonderfully poignant expression on his face, in which self-confidence and vulnerability seem uneasily balanced. The artist's perennial awareness of the fugitive nature of his own identity – that of everyone, by implication - is enhanced by the fluid speed of his brushwork. Rembrandt may have painted the picture in as little as a single day.

All pictures are self-portraits of a kind. Picasso implied as much when he remarked that "my work is like a diary: it's even dated like a diary" – alluding to his habit of inscribing the day and month, as well as the year, on his canvases. Thanks to his meticulousness, we know that Femme Endormie was painted on 4 February, 1931. The identity of the woman sleeping is no secret, either: she is Marie-Thérèse Walter, a young woman whom Picasso saw outside the well-known Parisian department store Galeries Lafayette one day in 1927 and promptly swept off her feet.

She became his lover, as well as his way out of an unhappy marriage (to Olga Kokhlova). What did the fifty-something artist see in his new, barely twenty-something muse? A statuesque and mysterious creature: a kind of goddess even, embodying youth and innocence and pure force of life. Picasso's embrace of Marie-Thérèse as a woman coincided with his turn away from the fractured and dissonant language of Cubism, and his corresponding move towards a classically inspired language of painting.

Impressionist & Modern Art

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The cataclysm of the First World War may well have had something to do with it. After so much real violence, the violent idioms of the pre-war avant-garde movements lost their appeal for many artists, including Picasso. To shatter and disturb seemed less important than to find wholeness, peace, repose: and what could be more peaceful than this image of a young woman sleeping? Yet still there is a sense that the peace belongs to Marie-Therese, rather than Picasso. Her dreamless sleep is an enigma to him, one that he observes but from which he is excluded. Her eyes are closed but his are open. Wakefulness is his destiny and his duty. The Spanish Civil War is just around the corner. Guernica is yet to be painted.

Auction sales, which bring together works from many disparate sources, inevitably make for unaccustomed bedfellows. All the more so when, as in the case of the present sale, works of art have been included from sharply varying categories that are normally kept apart: Old Masters; Impressionism and Modern Art; Modern British; and Contemporary Art.

The result strikes me as dizzying, disorientating but also exhilarating: an invitation to find (or create) new connections between objects created across a span of some 500 years and more. Viewing the assembled lots is rather like looking at the history of art through the jumbled perspective of a kaleidoscope - or finding it laid out in the scattered fragments of an incomplete jigsaw puzzle.

The pieces cannot be made to fit together, so each takes on the character of a suggestion. Several suggest the idea of a confession, some kind of intimate revelation. This is true of the Rembrandt and the Picasso, and also of Barbara Hepworth's lyrical and deeply melancholic sculpture of the mid-1950s, Orpheus, which was surely inspired by the death of her son.

It is true too of Louise Bourgeois's memorably angry mannekin, Arched Figure, of 2004. The sculpture was inspired by the arcane psychoanalytic theories of the late nineteenth century, but also operates as an arch parody of the pigeonhole, marked Hysterical Woman, into which Bourgeois herself had been unwillingly crammed as an aspiring female artist in the years before and after the Second World War.

I remember visiting her in her New York studio sometime around 2000 - she was already in her late eighties, but still full of energy - and asking her about a work-in-progress on exactly the same theme. Her response? "They treated me like a hysteric so I thought I may as well make sculpture about it." She cackled as she said it, thoroughly enjoying her status as a Grande Dame of the Postmodern Age. I had the impression that she spent much of her later career heartily enjoying having the last laugh.

Even if Picasso was right and no artist can escape themselves, they can look outside themselves. Turner did so when he painted Whalley Bridge and Abbey, the real subject of which is perhaps no actual building or group of buildings, nor the clothworkers kneedeep in the stream below them, but the way light is reflected in water.

Even this early in his career (the picture was painted in 1808) the artist has begun to sense that in such shimmerings, such fluid translucencies, some truth about the everchanging nature of the universe may be grasped and somehow preserved using coloured pigment on canvas.

A hundred and thirty two years later another Englishman, Stanley Spencer, found a piece of heaven (or so it seemed to him) in a cottage garden in Gloucestershire. It was 1940 and the skies would soon be full of warplanes; but he preferred to look down at a patch of grass seething with wildflowers, creating from it a masterpiece of what might be termed pastoral pacifism.

If Spencer was a late Romantic, heir to Turner and to Constable, Gerhard Richter might more accurately be described as a post-Romantic. His four-panel painting entitled Wolken (Fenster) of 1970 looks back to the Romantic skyscapes of the Northern European tradition, evoking the work of such nineteenth-century painters as Johann Christian Dahl or Caspar David Friedrich. But the mood of Richter's work is melancholic and elegiac. He paints, perhaps, with a saddened awareness of the multiple misappropriations and distortions to which the Romantic spirit had been subjected by the evil forces of the Third Reich.

His painting suggests that for a German artist with a conscience, the ideals of the Romantic sublime – so corrupted by history and politics – cannot simply be revived and reactivated. As his title suggests – its English translation is Clouds (Window) – he cannot paint a Romantic hymn to the transcendent sky. He can only see it as if through a glass, darkly. He observes and captures its beauty – fringes of cloud taking on the colours of the setting sun – but his feelings for that beauty are inextricably bound up with sorrow. Richter mourns for an innocence that has been lost.

Jump back in time once again, some 200 years this time, and we find Bernardo Bellotto, in the late 1750s, contemplating part of the cityscape of Dresden. He does so with such a combination of affection and detachment it is as if the place itself, on that day and at that time, has survived in the image that records it. Looking at the picture, I am reminded of what Ortega y Gasset once said about Velazquez: "this is not art, but life perpetuated".

On the subject of art imitating life, it can also work the other way round, as a later chapter in the history of Bellotto's art demonstrates. When visiting Dresden recently I was informed by a local architectural historian that his topographical views of the old town were so revered for their accuracy that they became prime references for restorers rebuilding the devastated city after the bombardments of the Second World War.

What other shards jump out from the kaleidoscope? A wonderfully spectral Miró of 1927, entitled Painting (Woman in a Red Hat), in which the woman in question floats in fragments within a field of dreams; and a Matisse from the early 1940s, Dancer Seated in an Armchair, full of sensuality, saturated with colour and executed with such speed as to blur the boundaries between painting and drawing.

A newly restored portrait of a man by Frans Hals, fresh as the day it was painted; a sackcloth-and-ashes Alberto Burri, arte povera so exemplary in its poverty as to be positively Franciscan; Fernand Léger's Still Life of 1914, an arrangement of forms on a Parisian cafe tabletop that seems to resemble a silo full of missiles, an image heavy with the threat of impending war.

In a yet more abstracting vein I find myself drawn to Kandinsky's joyfully explosive watercolour of around 1914-15, which is like a pantheist's firework display; to Lyonel Feininger's townscape of 1927, a vision of the world as crystalline and angular as the structure of a snowflake; and to Bridget Riley's shimmering veil of stripes, Cool Edge, of 1982.

Is Riley's true subject Nature (which would take her close to the Impressionists) or might it be the shifting movements of her own, human nature (which would make her more of an Expressionist)? Getting lost in her buzzing fields of colour, losing my balance, I wouldn't like to pronounce one way or the other.

Pure abstraction in painting is often said to have been invented by Kandinsky, but thinking about these works and the artists who made them it strikes me that the truth is more complicated. Some years ago I spent an hour or so walking around the National Gallery in London with none other than Bridget Riley.

We paused to admire the painting of drapery in Raphael's St Catherine of Alexandria. I remember her commenting on the play of colour energies in the saint's robes - crimson, blue, yellow and green - and have always remembered her words about it: "drapery is the abstraction of figurative art." It struck me then, and still does, as a wonderfully persuasive way of linking the sensibilities of the past to those of more modern times.

What more eloquent demonstration of all this could there be than Andrea del Verrochio's extraordinary drapery study for one of the key sculptures of the Florentine Renaissance, The Incredulity of St Thomas on the facade of Orsanmichele? Looking at this drawing, done in brush and wash, we can see the sculptor thinking about the drapery of the standing Christ and treating it, in essence, as an abstract pattern of forms - yet one that carries a precise charge of feeling and meaning.

Christ must be upright, so utterly grounded as to leave no doubt - even to Doubting Thomas - of the truth of His Resurrection. All this is conveyed in a columnar arrangement of linen, folded just so and stiffened with a mixture of plaster and water to keep its shape so that del Verocchio could make his drawing - and use it, in turn, to shape his eventual life-size sculpture in cast bronze. We know how this was all done because Giorgio Vasari, the father of modern art history, gave the recipe in his magnum opus, The Lives of the Artists. The result? A masterpiece of Renaissance abstraction, created circa 1468.

Like all the best works of art - like the Rembrandt I began with - what del Verrochio's drawing really represents is a moment of consciousness snatched from the continuum of life and preserved, as if by miracle, in the form of an image. I like the fact that water was an essential part of his medium. Montaigne was no doubt right when he said that human consciousness, changing through time, is as hard to grasp as water. But it also occurs to me that art is the best way we have (perhaps the only way) to stop the flow, for just an instant; and to glimpse, if not grasp, all that moves within.

Past Auction

Rembrandt to Richter

28 July 2020 | 5:00 PM BST | London