What do we have to keep in mind when utilizing literary theory in order to evaluate "Meeting at Night"?

"Meeting at Night" seems to be a simple love poem of twelve adventure-filled lines, yet critics have found significant comment, within these twelve simple lines, about Victorian society and culture and about the poetic persona's personal struggles. How much information the poem gives up depends—as with all literature—upon the literary theory used to approach analysis of its twelve lines. Analysis of "Meeting at Night" is made more complex because, being the first half of a pair of poems—with "Parting at Morning" forming the second half—a theme made evident in the second poem can seep over and influence analysis of the first. Whether this is correct literary analysis or not depends, again, upon the critical literary theory used to approach it.
Essentials of Literature's Theoretical Approaches
There are essentially two kinds of critical literary theoretical approaches. The first kind of theoretical approach is concerned primarily with the text itself, while the second is concerned primarily with externals, such as history, society, culture, and biography. These two basic kinds of theoretical approaches can be combined in various ways or can be used exclusively. To illustrate, Formalism uses exclusively text and Marxism uses Marxist theory to produce literary analysis, while New Historicism uses a combination of text, social, cultural, historical and biographical issues to produce literary analysis. Application of different theoretical approaches to a literary work, like "Meeting at Night," can yield sometimes very different results.