It has been calculated that there are more artists practising today than were alive in the whole Renaissance, all three centuries of it. But we are no longer following one storyline: we are in a new situation, where there is now no mainstream. The stream has flowed into the sea and all we can do now is to trace some of the main currents.
20th-century art is almost indefinable, and ironically we can consider that as its definition. This makes sense, as we live in a world that is in a constant state of flux. Not only is science changing the outward forms of life, but we are beginning to discover the strange centrality of our subconscious desires and fears. All this is completely new and unsettling, and art naturally reflects it.
The story of painting now loses its way temporarily: it enters upon an encounter with the unknown and the uncertain. Only the passage of time can reveal which artists in our contemporary world will last, and which will not.
We have dates in the 20th century, and pictures to attach to them, but there is no longer a coherent time sequence. This can be irritating to the tidy-minded, but it is in fact exciting in its adventurous freedom. With so many interesting artists, some of whom time may vindicate as of great importance, there is only space to touch briefly on those who seem to many observers to be part of the story, and not just footnotes.