PAUL CÉZANNE (1881-1973)
Still Life with a Peach and Two Green Pears, 1883-87 (oil on canvas)
Abstract Shapes, modified by the other visual elements, are the subject matter of Abstract Art.
When Paul Cézanne began to distort the perspective of representational shapes in his paintings, art took its first steps on a journey that led it through the partial abstraction of Cubism and Futurism to a range of pure abstract styles including Suprematism, Constructivism, De Stijl, Abstract Expressionism, Op Art and Minimalism.
In 'Still Life with a Peach and Two Green Pears' Cézanne tilts the perspective of the plate towards the picture plane. This has the effect of flattening the composition and emphasizing the abstract outline of its shapes. The flatness of the painting is further enhanced by the diamond shaped moulding and the circular handle of the cupboard in the background. Cézanne believed that the two dimensional qualities of a painting should not be denied and consequently much of his work involves:
- creating a balanced arrangement of shapes, some of which may be distorted for the benefit of the composition.
- defining depth and form with the natural properties of color, where warm colors appear to advance while cool colors recede.
- adapting his painting technique by using regulated brushstrokes to emphasize the unity of surface in his work.
Cézanne was not interested in the Impressionists' attempts to imitate the fleeting effects of light and color in nature. He called his paintings 'constructions after nature'  where the colors and forms that he observed were reconstructed as 'something solid and durable, like the art of the museum'. 
PIET MONDRIAN (1872-1944)
Broadway Boogie Woogie, 1942-43 (oil on canvas)
Abstract artists attempt to stimulate an emotional response by arranging the visual elements in a harmonic or dynamic configuration, much in the same way that a musician uses sound, pitch, tempo and silence to compose a piece of music. A musical analogy has often been used to help describe the effect of abstract art on the viewer.
Most people find it difficult to look at an abstract image without intuitively trying to interpret it through their understanding of representational forms. When looking at abstract artworks, the viewer often needs to take a transcendent leap and open their mind to the metaphysical properties of the visual elements, embracing a more spiritual response as opposed to an analytical one.
Piet Mondrian, the major artist of the De Stijl movement, was arguably the greatest exponent of 'pure' abstraction in the 20th century. Throughout many years of development he reduced the visual elements of his paintings to horizontals, verticals, rectangles and primary colors with black, white and grey. He gave his paintings objective titles such as 'Composition with Red, Yellow and Blue' to try to disconnect them from any representational interpretation. His art was an attempt to discover a new language of universal relationships whose visual harmony could somehow touch the human spirit.
One of his last great works, 'Broadway Boogie Woogie', is possibly the 'purest' of his paintings but its title paradoxically pulls us back into the realms of representation with its musical reference to Broadway in New York. Consequently it becomes very difficult to look at the work without relating it to an aerial view of the buildings and traffic flow through Manhattan. Once you have that image in your mind, the pulsing of the small squares becomes the movement of vehicles along the streets and colors such as yellow take on unintended references to New York taxis. Despite this representational distraction, it is a testament to the abstract qualities of this painting that it still retains the power to move us.
As a serious art form, pure abstraction is a rarified atmosphere. It requires the artist to look inwards with a rigorous discipline and to rely entirely on their own instincts and experience of the visual elements to inspire their creative vision. The representational artist has a far greater degree of freedom with both the natural and fabricated worlds accessible as the source of their inspiration, but the abstract artist has the unique opportunity to create something that has never been seen before. Perhaps the best art like 'Broadway Boogie Woogie' has a foot in both camps: it can create an idealized image that lifts the spirit but it also has a reassuring hold on reality.