"This insidious language"
Like any other poet, Shapiro worked with language. His poetry used language as a material, tool and subject of analysis; in a highly conscious manner, it explored the functions, effects, and imperfections of language. The poet once said in an interview that [his] ”poetry is an insidious private language, yielding an alternative to the public language of TIME magazine and TV. My art is intervention. My method is doubt (...) My poetry is just snowflakes.” This quotation shows that Shapiro weaponized poetic language and simultaneously acknowledged its limited impact on reality - short-lived and transient as a snowflake.
Language can bring about powerful associations or trigger action: words carry sounds, words convey meaning and possibly have consequences. And so, citing his hospitalized mother's words, Shapiro writes in a poem:
The worst words in the English language
Are these David - Don’t move
And what do you think the best words are: Here’s some water...
(To An Idea, p. 67)
In his writings, Shapiro often refers to Walter Benjamin, and appears to draw on the German philosopher's belief that literature is a rendition of a certain "pure language." In his "Task of the translator," discussing the possibility of translation from one language into another, Benjamin remarks,
Any translation which intends to perform a transmitting function cannot transmit anything but information - hence, something inessential. But do we not generally regard as the essential substance of a literary work what it contains in addition to information - as even a poor translator will admit - the unfathomable, the mysterious, the 'poetic,' something that a translator can reproduce only if he is also a poet?
When commenting on one of his poems, Shapiro revealed:
Music is my first language; language was my second language. Since my childhood, I liked to tear up language and put things back together like a broken ashtray. I grew up in a family of musicians, and my father preferred Bach and Rodin to science (...) You can call me a miniaturist, but I love putting long sequences together more like chamber music or unaccompanied sonatas (...) My favorite medium is eraser fluid and the human voice. Dear reader, if poetry weren’t music, how could there be songs?
This passage reveals a lot about Shapiro's language philosophy,* which is full of paradoxes: a miniaturist poet writing long sequences, being so careful about his poetic language, even though that language is only secondary to music. To my mind, the statement about eraser fluid is of particular importance as it shifts the attention from what is written to what could potentially be written. Shapiro was a self-limiting poet deleting whatever in his poems seemed unnecessary.

*language philosophy is a useful term I came across when reading about Polish poet Miron Białoszewski, and I decided to apply it to Shapiro's poetry as I noticed numerous parallels between the two poetics
