Like I said, I want to look at the following sentence from Chapter 6 of Nabokov's The Defence in some detail, in order to see how it accomplishes a phenomenologically correct description.
Only rarely did he notice his own existence, when for example lack of breath -- the revenge of a heavy body -- forced him to halt with open mouth on a staircase, or when he had a toothache, or when at a late hour during his chess cogitations an outstretched hand shaking a matchbox failed to evoke in it the rattle of matches, and the cigarette that seemed to have been thrust unnoticed into his mouth by someone else suddenly grew and asserted itself, solid, soulless, and static, and his whole life became concentrated in the single desire to smoke, although goodness knows how many cigarettes had already been unconsciously consumed.
I read the opening, "Only rarely did he notice his own existence," a bit like the "so much depends/upon" of "The Red Wheelbarrow", i.e., as a way of introducing some sense of a stake, which the image is then supposed to cash in. So we can take the word "existence" in the most philosophical sense available, namely, the Dasein of phenomenology. In Being and Time, Heidegger tells us that all phenomenology is finally descriptive, by which he means that it seeks the direct exhibition and demonstration of the phenomenon under investigation "in terms of the 'thinghood' of what is to be 'described'." (H. 35) Nabokov teaches us to avoid "involuntarily sinking into the history of that object" and rather to "stay at the exact level of the moment," that is, he describes "transparent things, through which the past shines!" (Transparent Things, Ch. 1) He describes their thinghood.
I'll skip the two minor cases of physical discomfort and propose also that the last reference to the unconscious tells needlessly what has already been shown. W're dealing with prose here and the sentence works just fine in context. What remains of phenomenological interest are the following items:
an outstretched hand shaking a matchbox
the failure to evoke in it [the matchbox] the rattle of matches
the cigarette that seemed to have been thrust unnoticed into
someone else [who seemed to have done the thrusting]
its sudden growth and assertion of itself, solid, soulless, and static,
his whole life
its concentration in
the single desire to smoke
One very interesting thing to notice at this point is the lack of any straighforwardly visual imagery. He could very well be blind and have this very same experience. It is not a visual image (like the wheelbarrow's glazed redness).