In literature, a conflict can be defined as any struggle between two opposites; most often, the protagonist struggles against the antagonist. Since a conflict is a struggle, or a fight, we can easily describe conflicts as something vs. something else. Common conflicts include character vs. character, character vs. society, character vs. nature, and character vs. self.
Randy Pausch uses the non-fiction work The Last Lecture, as well as the lecture the book was based off of, to teach his audience how to overcome obstacles in order to fulfill childhood dreams. Hence, one dominant conflict found in the work can be considered character vs. obstacles; sometimes those obstacles have to do with nature; sometimes they have to do with society.
The first obstacle the reader learns about concerns the fact that Pausch has been diagnosed with pancreatic cancer and has only three months left to live. He also still has a lot to live for, including a strong career, three children, and a loving wife. Hence, since Pausch's cancer is impeding him from doing what he wants to continue doing, his cancer also serves as a conflict. Plus, since cancer and death are natural occurrences, we can say that the conflict is character vs. nature.
The conflict of character vs. society is also revealed through the stories he uses in his lecture to instruct his students on how to fulfill childhood dreams. For example, one of his dreams was to achieve weightlessness in space. He partially fulfilled this goal by working with a team to create a simulation aimed at helping people overcome nausea experienced during weightlessness. However, fully achieving his goal was also temporarily thwarted when his university would not permit faculty to enter the simulator; only journalists and students could enter the simulator. He overcame this obstacle by quitting his job and being hired as a journalist. Hence, the university's decision to forbid faculty from entering the simulator also serves as a conflict, and since a university is a part of society, we can call this conflict character vs. society.
Throughout the book, many other obstacles he speaks of overcoming also have to do with society, so many other conflicts are also character vs. society.