In “Meeting the Universe Halfway”, Karen Barad develops the theory of agential realism and posthumanism on the basis of the laws of quantum physics. Posthumanism means that the human being is placed back into the world and participates in the becoming of the world through intra-action with the other. The purpose of the thesis is to present Barad’s theory in relation to the laws of quantum physics and discuss the ethical implications of her theory, and then to explore how the good life could be defined from a posthumanist perspective. The discussion of the good life is conducted in dialogue with Plato’s text “Gorgias”. In “Gorgias”, two different views of the good life are presented: a life aimed at satisfying one’s desires at the expense of others, and a life of moderation and justice, which Socrates advocates. When the posthumanist perspective is introduced, it shows that these definitions are limited to the individual. The posthumanist perspective opens up a broader view of the good life. It shows that the life experienced by the human being in intra-action with the other is a greater life than her individual life alone. However, for the posthumanist perspective to lead to a better life, it requires that human beings act ethically.