“Having heard without comprehension they are like the deaf; this saying bears witness to them: present they are absent” (here K 2; cp. WF 5, DK B34, W 55).
Again, the metaphor of speech is at play. An utterance occurs in time. Before the final word of an utterance is heard the first part of the utterance has disappeared. Indeed, before the final tone of a word occurs, the first tone has disappeared. What is present is mere tonality. It is only through an act of the intellect, constructing meaning from tones once present but now absent, that meaning is possible, that comprehension is possible. The senses deliver tone. The mind delivers comprehension and meaning. Those who may have comprehended have a reserve of meanings and understandings that they can call forth — ideas, comprehended and now accessible in memory to again called into presence from their absence. Those who are present while present draw on these meanings and understand.
But here, the talk is of those who do not comprehend. They are like the deaf. Those who do not understand meanings and do not comprehend might as well have not heard the tones. Those who comprehend understand the tones against the background of meanings which they have bring to the present.
What are those who do not comprehend present to? Tones alone. To what are they absent? Meaning, comprehension. Meaning and comprehension, for their part, paradoxically require being present to what is momentarily absent, present to what is absent from the senses, but to what gives the sensory tone its meaning. Comprehension requires being present to an internal world of meaning. Being present to a communication requires a synthesis of the external and the internal. The tones must be synthesized into words that are meaningful, understood against the web of other words with meanings that are present to the intellect. Those who do not comprehend are not present to the world of inner meaning.