In what ways do the ideas thoreau presents in paragraph 6 become the foundations for the beliefs he expresses in paragraph 7? for instance, how do the ideas explained in paragraph 6 lead to his exhortation, if the engine whistles, let it whistle till it is hoarse for its pains?

Thoreau appeared to both a pacifist and a rebel in this passage. He says in paragraph 7 to go at one's pace and to not answer the call of society just because one feels obligated. He is saying that we should not fret over something just because it is present and others fret over it. He sets this up in paragraph 6 by saying if man would just stop for a second and consider what is permanent and not fleeting (the temporary pain, problem), then he would find all that is important are things of great important and permanence. So he says to the whistle that it can just continue to, well, whistle. He realizes the great truth that he cannot control what others do, or what things cry for attention, but he can certainly control whether or not let reacts to it.