I see three persuasive techniques employed in this essay. The first is Thoreau’s method of making this piece a personal plea. He uses “I” a lot. He tells us what he thinks, prompting us to consider what we may think about the same issues.
I think that we should be men first, and subjects afterward.
The only obligation which I have a right to assume is to do at any time what I think right. (both from paragraph 4)
Next are Thoreau’s reports of his own interactions with the law and government. Up to this point, he has been talking theoretically. Now he switches to sharing some details of his own encounters. The first time was when he was billed to help to pay the salary for the town parish minister (as all town residents and members of the congregation of the sole church were, at the time). He claimed that he was not a member of the congregation; and sure enough, he was no longer sent this bill. The second time was when he was put in jail overnight for non-payment of the state poll tax. A relative ended up paying the tax for him; but his intent and unique experience were the key points of the action. When he presented this essay as a lecture, these were probably the parts his townsmen and listeners most wanted to hear.
Some years ago, the State met me in behalf of the Church, and commanded me to pay a certain sum toward the support of a clergyman whose preaching my father attended, but never I myself. (paragraph 24)
I have paid no poll-tax for six years. I was put into a jail once on this account, for one night, and … I could not help being struck with the foolishness of that institution which treated me as if I were mere flesh and blood and bones, to be locked up. (paragraph 25)
Finally, Thoreau asks questions of his audience, in the sections before and after his jail story account. He no doubt hopes these will prod people to think more deeply about how the American system of government is set up to work.
Can there not be a government in which majorities do not virtually decide right and wrong, but conscience? (paragraph 4)
Is a democracy, such as we know it, the last improvement possible in government? Is it not possible to take a step further toward recognizing and organizing the rights of man? (paragraph 44, the final one)