Why, in the poem "Stopping by Woods on a Snowy Evening," does the speaker consider the woods dark, deep, and lovely?

In "Stopping by Woods on a Snowy Evening," the speaker describes the way in which the "woods fill up with snow" (line 4).  There is nothing around him, no "farmhouse near" (6), and it is very, very dark because the poem is set on the "darkest evening of the year" (8).  All is quiet around him with only the sound of an "easy wind" gently blowing the "downy flake[s]" in the air (12).  The speaker...

In "Stopping by Woods on a Snowy Evening," the speaker describes the way in which the "woods fill up with snow" (line 4).  There is nothing around him, no "farmhouse near" (6), and it is very, very dark because the poem is set on the "darkest evening of the year" (8).  All is quiet around him with only the sound of an "easy wind" gently blowing the "downy flake[s]" in the air (12).  The speaker is arrested in his progress through the woods because the scene around him is so incredibly beautiful. 

When the speaker describes the woods as "lovely, dark and deep," it seems to be in recognition of all of these things (13).  It sounds like such a serenely peaceful moment, a moment when he simply pauses and takes in all the natural beauty of his surroundings.  Further, the next line helps to illuminate why he has been so struck by the woods tonight: he has "promises to keep" (14).  In other words, he has obligations to fulfill, things that he must do, and places that he must go.  The business of the "village," perhaps, or just of normal, daily life, is juxtaposed with the tranquility of the forest, and the woods seem that much more deep and lovely as a result of this contrast.  Moreover, he has "miles to go before [he] sleep[s]," an awareness of how much more he has yet to accomplish, and that makes the woods seem so very inviting as well (16).  He seems to wish that he could just stay there, where it is "lovely" and "dark" and he has nothing to consider but the night, but he cannot.