armchair theory; speculative argument; an idea with no practical importance

thought / opinion / idea

application of something

to apply

pure, unmixed, genuine / selfless, pure / innocent

purity / selflessness, purity / innocence

on the desk / being on paper, (being no more than) armchair

he / distal demonstrative, something far off removed from both speaker and listener: that / boyfriend

distal demonstrative, something far off removed from both speaker and listener: that, yon / particularly, male personal third person pronoun: he / by extension from he: boyfriend

he; boyfriend