The problem with language, then, is that it has a double task. First, it must communicate the common, everyday work of the world. Second, it must communicate the deep, essential truths about Dasein. We have to use the same language to tell a barber how to cut our hair as we do to engage and describe the essence of beings. The advantage to this is that many of the world's deeper insights are available to any who pass the initial test of speaking a common language. The disadvantage is that common language can be used too easily, causing the speaker and the listener to trivialize assertions. A common example that Heidegger uses is "the sky is blue." We hear that assertion all the time, but what does "is" mean in that statement? How does it unconceal? Is it metaphorical or literal? We find no pat answer when we begin to truly think about it, but instead fall easily in "erring," fleeing from the "mystery toward that which is readily available."
Poetry comes as an answer to the difficulty, standing as a sort of golden mean between language too familiar and language too removed. Careful use of syntax and diction allows the poet to uncover beings because readers must think about every word, especially the simple words. This becomes apparent when we think about the difference between reading a common novel and reading a compendium of poetry. We can breeze over the words of novels, accessing just enough to follow a plot and understand an occasional image. We may also breeze over poetry, but conscientious readers do not, for they realize that uncovering comes eloquently through allusions, syntax, and unusual metaphors.