When referring to abstract noun how should I use demonstratives? Abstract nouns do not have a distance from the speaker. For example when should I say "this story/concept/word/name" and when I should say "that story/concept/word/name" or "the story/concept/word/name""?
While you can argue that because abstract nouns cannot been seen or touched, they do not have a physical distance from the speaker, in many cases they still exist in some form, or are exhibited or physically manifested in some way. Thus you can still use 'this' for abstract nouns which exist closer to the speaker (or listener) in space or time.
This knowledge can help you. (closer in distance or time)
That knowledge they posses can help them. (further in distance)
That knowledge was forgotten. (further in time)
This fear must be controlled. (closer in distance or time)
That fear caused you to run. (further in time)
If you are referring to it directly, you would say 'this':
I'm going to tell this story.
If you are referring to it, but it is not the important subject of the sentence, you would say 'that':
I'm going to tell this story, instead of that story.
I should also add a note about informal circumstances. When, say, two people are discussing a concept, the concept is personified, and is given a distance.
Person A talks about a concept of theirs. When Person B refers to the concept, he would say 'that concept' because the concept belongs to Person A, or is 'standing by' Person A.