�Beauty is the mystery of life. It is not just in the eye. It is in the mind. It is our positive response to life.� Agnes Martin, 1989.
How good to be released from all the words of reading and writing: by walking or swimming or looking at art. Sometimes a particular episode of release works especially well. This seems to involve (for me) enlarging the space the mind inhabits and changing its shape. The Agnes Martin exhibition at Tate Modern has just done that.
Martin painted and drew using grids: square, oblong, huge or small, marked or scored by lines of graphite or occasionally by dots; often filled, in the big paintings, with pale horizontal bands of paint.

(I�m wary of reproducing images, so am illustrating this with book covers. If you google images of Agnes Martin paintings there are plenty on gallery websites.)
From these late paintings the exhibition takes one back to her early work, her journey towards formal abstraction via Mir� here or Rothko there (always fascinating, an artist�s journey to mature style), and through a roughly chronological survey�

The mind soon gets accustomed to minor variations, and geekily delights in them; so when confronted by a pair of black pyramids with lime green tips or a huge gold-leaf square on which a grid of horizontal oblongs is scored (�Friendship�, see here), it�s a shock.
John Ashbery once described Agnes Martin�s work as �almost distressingly powerful.�
On one grey horizontal banded painting the paint forms liquid patterns as if blown across the canvas. These look like clouds though clouds, however liquid, never look like that.
An inner room holds a series of twelve large paintings, The Islands, all variously banded in shades of white. I was in there on my own�
It was impossible not to search for the human eye, hand, mind in each picture, in a pencilled line�s wobble on the bumpy canvas or a change in the density of paint.
There were several paintings which contained wide greyish horizontal bands with a narrow pale strip between each. Soon I was seeing these as sea with narrow land on the horizon, then sky� then land above the sky, more sea above that, then land, then sky.. like a stuck film reel that flickers between frames.

I came out looking hard at the floor of wooden planks, at how paving stones intersect, at drains in the gutter. At the gridmarks of the pedestrian bridge and the Renaissance-city view of St Paul�s it opened up. At bands of river and land and sky. At the world. �I paint with my back to the world�, Martin said.
Agnes Martin is at Tate Modern until 11 October.