Thoreau incorporates pathos in many passages in Walden to provoke readers' emotions and encourage them to believe in his philosophical vision. Pathos— which is just one of three "modes of persuasion" in rhetoric—can clearly be seen in the following passage from "Solitude":
Yet I experienced sometimes that the most sweet and tender, the most innocent and encouraging society may be found in any natural object, even for the poor misanthrope and most melancholy man. There can be no very black melancholy to him who lives in the midst of Nature and has his senses still. There was never yet such a storm but it was Æolian music to a healthy and innocent ear. Nothing can rightly compel a simple and brave man to a vulgar sadness. While I enjoy the friendship of the seasons I trust that nothing can make life a burden to me.
In this passage, the author tries to make inanimate ("natural") objects seem emotionally relevant. Examples of pathos include phrases like "sweet and tender," and "encouraging[...] even for the poor misanthrope." Some examples subvert traditional expectations—one would think to fear a storm, but he calls it "Æolian music." Thoreau's main point here is that any person can find joy and hope in nature, and everyone should befriend Nature in all of its forms.
In order to advocate for a life of solitude, Thoreau must make it seem less lonely. Here and elsewhere in the book, he uses pathos to evoke the emotional bond among all elements of nature, including those that seem inanimate or irrelevant to everyday life. By referencing a range of feelings, Thoreau encourages the reader to sympathize with his case for a simpler, more natural way of life. His philosophy of simplicity goes against contemporary sensibilities of urban life, so he employs this form of rhetorical persuasion to change the average person's mind.