He saw that there could be no innocence if one could not acquire experience and knowledge later. This is also true of the kind of art Blake executed. Engravings are drawings made up of lines. It is not possible to remove the lines and have any art left, because that is what his style art does: it divides blank space. Without the blank space, there can be no lines. Without the lines, there is no art. There is only a blank sheet. Blake emphasizes the differences between his poems of innocence and poems of experience. Just as Blake could have painted in watercolors, with many colors, many shades, all running together, he could have imbued his poems with "shades of gray." When artists paint with colors, they don't use line. The line is implied as the rooftop meets the sky. But in Blake's etchings, the only way we would see the separation of roof and sky is because Blake drew it as a line. Blake took his poems and boiled the concepts down to their core, eliminating uncertainty and doubt and leaving the images and the ideas as clearly defined as possible. He did the same thing with his art. He was the opposite of an impressionistic painter who might paint a tree by putting small dots on the paper and letting the viewer's eye add the lines. For Blake, the line, the separation between tree and not-tree, drawing and empty space, was important. It was the essence of the tree for him.

In his poems of innocence and experience, he made this very clear by speaking of two muses. For his poems of innocence he spoke of a childlike muse. He includes his theology in these poems, but it is a childlike, innocent view of God as gentle and loving. However, later he...

Just as we cannot look at a drawing of a tree without taking in the empty spaces, he sees God as defined by both the gentle and fear-invoking qualities he sees in God.
As Blake draws the lamb and the tiger for us with words, he creates the kind of tension and balance seen in good art. In well done art, the rendering goes beyond a literal representation of the thing to something that transcends the reality of the object depicted and gives us new insights about it. Blake does this with his poetry by drawing clear lines between things while showing their inter-relatedness - the line drawing, along with the space the line splits, are both crucial to the drawing. The drawing cannot exist unless both are there. It is not possible to draw without dividing space. He makes a similar distinction between innocence and experience, between the lion and the lamb. Could we fully appreciate the gentleness of the lamb (both as the animal and as one aspect of God) without also fully appreciating the strength and ferocity of the tiger (also as one aspect of God)? Could a God who was only lamb-like save us from a force as powerful as Satan?

Perhaps good cannot triumph over evil without fully understanding evil. Perhaps evil cannot be defined if we do not know what the lack of evil is. Blake used the words in his poems in the same way an artist uses line in drawings - to make differences absolutely clear. Those differences help define their opposites. Blake used words, like lines on paper, to highlight and dramatize opposites to make the meaning of both more clear.