What does Henry David Thoreau mean when he says, "In accumulating property for ourselves or our posterity, founding a family or a state, or even acquiring fame, we are mortal; but in dealing with truth, we are immortal"?

Henry David Thoreau, in this quote, is drawing a distinction between material pursuits and the pursuit of truth. When Thoreau refers to the act of accumulating property, founding families or states, or even acquiring fame, he categorizes these activities as mortal. This means that they are temporary and tied to our physical existence. These are endeavors that are transient, and they end with our death; they are finite and linked to societal and earthly measures of success.

On the other hand, Thoreau suggests that in "dealing with truth," we engage in something that transcends our mortal existence. Truth, as Thoreau sees it, is an eternal and universal concept that does not perish with the individual. Engaging with truth, seeking it, and understanding it, according to Thoreau, connect us with something that surpasses the limitations of life and death. It's essentially a spiritual or intellectual pursuit that allies us with the immortal, the permanent. This view reflects Thoreau's broader philosophical beliefs which emphasize the importance of individual conscience and the profound connection between the self and the universal truths.

Thoreau is encouraging individuals to focus on higher principles and truths rather than on temporary material or social achievements. In seeking and aligning ourselves with truth, we touch upon something that is immortal and lasting, which can imbue our actions and our existence with greater meaning.