Demonstratives typically evoke pointing at something perceptible, but the source recognizes their application to what is not directly available to the senses, especially when it is already present in thought or discourse.
Visible referent: «هٰذَا الْبَابُ مَفْتُوحٌ» — pointing to a door and saying “this door is open.”
Mental referent: after developing an argument, «ذٰلِكَ أَصْلُ الْمَسْأَلَةِ» — “that is the foundation of the issue.”
Reference to a non-visible subject remains meaningful when supported by memory, convention, or the preceding discourse. A relevant contextual cue makes the referent recoverable.