Sentence:  Finally , just as no different issues are posed for thoughtful analysis by the foreshortening of time that may yet pass before the end of human life on this earth , but only stimulation and alarm to the imagination , the same thing must be said in connection with the question of what we may perhaps already be <WSD>doing</WSD> , by human action , to accelerate this end . 
Meaning of the word marked with <WSD> tags:  carry out or perform an action