In general, theory (Greek, theoria) is a cognitive state suffused with some kind of affect (emotion). Theory is a questioning attitude towards reality and towards pregiven thoughts (assumptions). It is also a feeling of wonderment. Philosophy's basic affect is wonderment (Plato, Theaetetus).
Then there is “theory.” Which is what we mostly know from English Lit. and Comp. Lit. classes.
“Theory” is really a very small bandwidth of continental philosophy (i.e. not analytic, mostly English and USA) that literature scholars have latched onto since about 1950.
Quite often, because of this selectiveness, and because of the forgetting that selections were made by someone somewhere; and because of disciplinary chauvinism: “theory” (which is not singular at all, really) has often proclaimed that it is bigger than, or beyond, or above, or more radical than, philosophy.
Not true! That's a bit narcissistic if you think about it. Precisely because they work in big, powerful departments (mostly, at least compared with other humanities ones), English scholars should get out more…
Also, this splendid isolation has led to a not so great syndrome: the use of “theorists” as candy sprinkles on an essay.
In this class, we shall study a much broader bandwidth of philosophy to find out about aesthetics, which are the basis of all theory.
We will be taking the approach of a committed scholar, rather than the overview approach. Not an ism a week, then.