Why does Thoreau compare soldiers and other who serve the govenment to wood and earch and stones?

- When a man no longer uses his conscience he becomes a robot.

Explanation:

Henry David Thoreau, the famous philosopher and essayist in his famous and one of the most acknowledged work 'Civil Disobedience' is a critique to he practices like 'slavery' and 'Mexican-American war'. He encourages the readers to give priority to their conscience over all the 'dictates of laws' proposed by majority.

Thoreau compares the soldiers and other people who follow or obey the government to 'wood, earth, and stones' as he feels they have no liberty to exercise or pursue their conscience or morality and thus, they become like robots or machines. They are like the tools (machines) who do not possess a thought or conscience of their own and blindly follows the instructions (as offered by the government). Thoreau asked the people to follow their conscience and do what they feel to be right instead of relentlessly following the orders of the government.