Flashbacks are an important storytelling device in "Breaking Bad," and we can use them to explain some of Heidegger's ideas about being and time. Heidegger believes that being emerges from a unity of past, present, and future, with our actions in the past setting out a number of possible futures for us. He says that a human being's past is never really left behind; it lingers and influences who we are in the present and who we might possibly be in the future.
"Breaking Bad"'s flashbacks show us the moments in Walt's life before he became the mythical, meth making and dealing Heisenberg. When viewed in this light, the flashbacks become more than just a means of telling the story. Their philosophical significance comes from the fact that we're given brief but telling glimpses of the man that Walter once aspired to be (for Heidegger this is one of Walt's possibilities): the renowned chemist who could provide for Skyler and Walt Jr. while at the same time enjoying all the material trappings that the American Dream has to offer.