Answer:
Being self-sufficient dramatically reduces one's standard of living.
Step-by-step explanation:
Thoreau had a view that one should go into the woods, live simply and produce what you need with your own hands (be self-sufficient).
Economists explain why most people in the United States do not do this. To an economist everyone in society have their own specialisation. That is why they emphasize division of labour.
So going into the woods to be self-sufficient is not the best use of one's resources and abilities.
Everyone has something unique to contribute in an interaction. What I have comparative advantage producing will be difficult for another person.
This will create a network of people giving what they have comparative advantage producing in exchange for goods and services they do not have competitive advantage producing. This results in everyone maximising utility.
But Thoreau's view will not maximise utility because it is not possible you have advantage producing all you need.