What you are thinking about is not in your brain.
When one begins to explain the perception of the blackboard from
sensory stimuli, one has indeed seen the blackboard. In this theory of
sensory stimuli, where is [there a place for] what is meant by "is" [being] ?
Even the greatest possible accumulation and intensity of stimuli will never
bring forth the "is." [What is meant by it] is already presupposed in every
[act of] being stimulated.
Even imagining can only be seen as directed into a world [in eine
Welt hinein] and can only happen into a world. To imagine a golden
mountain can always really only happen in such a way that even this
[mountain] is somehow situated in a world. Even in such imagining there
is more there than just the isolated golden mountain. I do not imagine a
golden mountain within my consciousness or within my brain, but rather
I relate it to a world, to a landscape, which in turn is again related to
the world in which I exist bodily. The golden mountain is present as
something imagined which is a specific mode of presence and which has
the character of a world. It is related to men, earth, sky, and the gods.
The whole starting point within the psychic and the point of departure
from a consciousness is an abstraction and a nondemonstrable construct
[eine nicht ausweisbare Konstruktion]. The relationships of a thing to the surrounding
world [Umwelt] do not require explanation; they must simply
be seen [in a phenomenological sense].