In the poem "Snow" by Louis MacNeice, the last two lines are more abstract in nature.
"On the tongue on the eyes on the ears in the palms of one's hands -
There is more than glass between the snow and the huge roses."
They lend themselves to imaginative thought as to what the author is really trying to say to his readers. There is room for conjecture and debate in these last two lines, hence their abstract quality. The lines can initially be read as concrete statements, but they are so much more. It is the pondering of what MacNeice intends with these lines that moves them beyond simple matter-of-fact statements.
MacNeice is subtly challenging his readers to see what separates the cold stark beauty outside from the warm, vivid, and vibrant beauty inside. The experience of the snow and cold is really only physically separated from the experience of the fire and the roses indoors by glass.
However, our perceptions--gained through our senses of sight, sound, taste, and touch--color our views of snow and roses. Our preconceived thoughts, prejudices, beliefs, ideals, views, and opinions are really what shape our perceptions of snow on the outside and roses on the inside.
This, by extension, applies to many areas of our life. We put up personal barriers, whether physical, or of the mind, that contribute to the way we see things. We may put up a fence as a physical barrier; we may be steadfast in a belief so that we separate our belief from another's, based on the internal conversation we have within ourselves and influenced by external stimuli.