The great nineteenth-century landscape painter J.M.W. Turner (who himself painted several watercolours for Paradise Lost) proposed in one of his Royal Academy lectures that 'the greatest richness of verse is often the least pictorial'. As Turner implies, Milton's poetry is at once vividly visual and extremely hard to visualize. Take the panorama of Hell that faces Satan upon his fall:

At once as far as angel's ken he views
The dismal situation waste and wild,
A dungeon horrible, on all sides round
As one great furnace flamed, yet from those flames
No light, but rather darkness visible
Served only to discover sights of woe...  (I.59)

In words like 'views', 'sights', 'visible' and 'ken' (now a rare word that means the range of someone's vision), Milton is repeatedly telling us that there is something to see here. First he sketches out some of the traditional topography of Hell: it is 'waste and wild', a 'dungeon horrible' filled with fire. But as so often in Paradise Lost, Milton's description of the scene turns upon a simile - 'As one great furnace flamed' - and, more particularly, upon the following word 'yet'. Milton's simile conjures up before the mind's eye the image of a roiling furnace, before saying 'no, Hell is not as simple as this'. We can only see Hell's fires by putting together in our imaginations two things that, in reality, are totally opposed. This is what Milton does in the famous oxymoron that gives this website its name: 'darkness visible'.

Illustrators of Paradise Lost have tried in various ways to represent these infernal fires. The artist of the 1688 edition tips his flames with black, bathing the fallen angels in a stark, unnatural light. William Strang's etching of 1896 creates a billowing curtain of fire that engulfs the whole composition. Yet what these efforts demonstrate, perhaps, is how unequal the human mind is to the task of imagining a region fiercely illuminated by the absence of light.