Whether or not literary criticism should be considered a separate field of inquiry from literary theory, or conversely from book reviewing, is a matter of some controversy. For example, the Johns Hopkins Guide to Literary Theory and Criticism draws no distinction between literary theory and literary criticism, and almost always uses the terms together to describe the same concept.
Criticism is
the study, evaluation, and interpretation of literature
(ibid.), while theory is
the systematic study of the nature of literature and of the methods for literary analysis.
Admittedly, "literary analysis" links back to literary criticism. But the most helpful way to define these terms - so they can refer to different things both worth being able to refer to, without the names being misleading - would be something like the following:
- Theory can deduce facts about authors' techniques and their conscious and subconscious intent, including their awareness of likely and intended effects on consumers. It would not judge such intentions and techniques (but see below).
- Criticism can document and explain specific opinions about the quality of a work. It need not imply such opinions are "correct", but it can understand the thinking that underlies them, and may even predict their likely prevalence. For example, one would hope literary criticism can make sense of why Shakespeare's works are widely considered among the best in English literature.
Insofar as there is a controversy over whether criticism and theory are even different in the first place, there is either a desire not to define the concepts in the above manner, or a recognition such definitions cannot be expected to match or become how the terms are widely used. (In particular, the aforementioned guide uses both terms, but makes no effort to make them non-synonymous, even though this could let us refer clearly to more ideas.) But none of that changes the following indisputable facts:
- Opinions about works' qualities are common, whether or not they're "correct" contra Hume;
- Some such opinions are more popular than others, especially with specific types of people;
- All this happens as a psychological result of how people react to works they encounter.
Is there a controversy over it being worth trying to theoretically make sense of these details, over it being worth separating such an effort from other aspects of analyzing literature, or over whether this is the right way to bifurcate these ideas? To me, it seems straightforward and helpful to distinguish between study of the positive and normative. (Other fields, e.g. economics, have no problem with this, even though normative assessment has to cite some positive facts.)