Since the days of Hölderlin and Schiller, poetry and "theory" have been the same thing. A neoclassical idea of poetics (to simplify greatly) is based on prescriptivism. Let's take Horace as a convenient example, or Boileaux.
Voulez-vous du public mériter les amours?
Sans cesse en écrivant variez vos discours.
Un style trop égal et toujours uniforme
En vain brille à nos yeux, il faut qu’il nous endorme.
On lit peu ces auteurs, nés pour nous ennuyer,
Qui toujours sur un ton semblent psalmodier.
It's pleasant advice for writers, or a set of rules to follow. How to please the public!
Aristotelian "Poetics" [Peri poetikes] was taken as a handbook rather than a work of literary theory, as we would understand it today. Here's Lope channeling Aristotle:
Ya tiene la comedia verdadera
su fin propuesto como todo género
de poema o poesis, y este ha sido
imitar las acciones de los hombres,
y pintar de aquel siglo las costumbres:
También cualquiera imitación poética
se hace de tres cosas, que son, plática,
verso dulce, armonía y la música,
que en esto fue común con la tragedia,
sólo diferenciándola en que trata
las acciones humildes y plebeyas,
y la tragedia las reales y altas.
Mirad si hay en las nuestras pocas faltas.
With romanticism, something fundamental changes. Sure, in these examples of "poetics" we see that verse (a poetic medium) is used to talk about poetry itself. This is quite different, though, from the romantic and postromantic idea of "poetics," a discourse about the inner nature of poetry from the inside. It doesn't even have to be written in verse any more, because poetry no longer needs verse to be poetic.
So "poetics" becomes writing about poetry in prose (often), like the essays of Lezama Lima, Robert Duncan's HD Book, or Lorca's "Juego y teoría del duende." Heidegger's late writing on poetry also belongs to this genre. He is thinking through language, and the language cannot be separated from "meaning."
Now in structuralism, there is a rebirth of the term "poetics," with a quasi-scientific meaning: the system of what literature is. Todorov's Poetics of Prose. It is not advice for the writer, but a systematization of what we know about literature. It is a return to Aristotle, in the sense that poetics means philosophical knowledge about poetry, not lame-ass Horatian advice.
But in the modern literary theory derived from Heidegger (Derrida, María Zambrano), the difference between poetry and theory disappears. If Lezama is a poet in his prose essays, than why isn't Zambrano or Derrida? Celan's poetics seems Heideggerian, if we look at Gadamer's essays on him.
Poetics is also the implicit theory of poetry embodied in the poems themselves. So Vallejo, who didn't write Lezama or Lorca-like essays, also has a poetics. The "Arte poética" of Neruda happens to use a neo-classical title, but it doesn't tell you how to write a poem. Huidobro's is more of a manifesto. The manifesto is another genre that comes to prominence with the avant-garde, another way poetics gets expressed. Look at how romantic Huidobro is in this poem. The idea of creativity in "creacionismo" comes straight from romanticism, which overthrew Aristotelian mimesis in favor of the creativity of the artist's mind. Wordsworth in "Tintern Abbey" is not imitating nature, but deriving his poetics from the ways in which his mind interacts with it.
Modern French theory is also linked quite explicitly to the avant-garde. Barthes and Kristeva and Sollers. Avant-garde theory is poetics in another form, once the pseudo-scientific structuralism wilted away in favor of neo-Heideggerian poetics.
The purpose of this course is to allow you to put everything together: see how theories fit together (or don't). Otherwise we just have a list of theories side by side. The consequence of the fusion of poetics (theory) and poetics (thought about poetry within poetry, or by poets) is that we could just as easily (well, not really easily!) use poetry to explain theory as vice-versa. In other words, the theorist doesn't stand above the poet explaining what she is doing. Lorca is a theorist, and Barthes is a poet.The theory of literature is internal to literature itself.