Since there is no objective consensus about the "Holy Spirit", it can not be considered a "truth about reality". Rather, it is an individual fantasy.
The term "Holy Spirit" is open to definitions before one can say anything about the concept.
The concrete denotation, the actual meaning of the word "holy" is "separate."
In that sense, if one will accept the suggestion, for argument sake here, that Truth is an archetype that has evolved, experiential, in man, then it is separated de facto fantasies and false impressions, erroneous perspectives, and out right lies are separated from that "idea" of a source inside our mind that KNOWS the truth.
My argument for this source is that it refers to the Unconscious mind.
The argument I would make is that, the Unconscious mind is reconstructed genetically, and born again into the generation of the living.
It is inaccessible to our Conscious mind,but is wide awake and interacting in our own affairs and the affairs of those around us all the time,... unbeknownst to us, consciously.
It is that ancient of the ancients to which Daniel and Revelation refer.
It is the Good Shepherd in our lives evidenced by emotions and instincts that come into our consciousness unbidden, as messengers (angels) who interject ideas into our dreams and our thinking as if from some outside source.