There seems to be agreement even among people who do not read Heidegger that Being and Time is one of the most important philosophical works of the twentieth century. Published in 1927 when Heidegger was thirty-six years old, the book represents an intensive effort to bring together a number of seemingly conflicting intellectual traditions, including, among others, those of Aristotle, St Paul, St Augustine, Luther, Kant, Hegel, Kierkegaard, Nietzsche, Bergson and Husserl. Being and Time can be read as a response to the domination of the theory of knowledge in modern philosophy since Descartes (Guignon 1983). While the most influential thinkers in Germany at the time, the neo-Kantians and positiv-ists, were trying to give an account of how we come to know the world, Heidegger set aside questions about knowledge and turned directly to an examination of the Being of entities.

Moreover, as the title of the book shows, the account of Being presented there stands in stark opposition to one of the central assumptions of mainstream Western philosophy: the assumption that Being must be thought of as something permanent and unchanging. Whereas most philosophers since Plato have assumed that the Being of anything must be understood in terms of what is eternal and fixed (Forms, essences, scientific laws, etc.), Heidegger suggests that Being is temporal unfolding; indeed, it is time itself. As Heidegger only finished half of Being and Time, we cannot be sure how he envisaged the final connection between Being and time.