Being and Time is Martin Heidegger's most influential book and one of the most important books in 20th century philosophy.
In "Being and Time" Heidegger attempts to reshape the way in which philosophy thinks about the concept of "being". The book critically reviews different methodological currents in philosophy to demonstrate their shortcoming in answering the question of being. According to Heidegger, philosophical prejudices not only shape the entire intellectual history of the West, but also determine our everyday understanding of ourselves and the world.
The Meaning of Being
The main topic of "Being and Time" is the "Question of the meaning of being in general". Heidegger asks about ontological being, i.e. about what is. But he also asks what it means to say that something "is", what it means to be. "Being" for Heidegger is something mutual to all different phenomenological appearances, and that thing is meaningful references. For example, a hammer and a nail are things which gain meaning by the manner in which people incorporate them into their purposeful actions. In asking about the meaning of being Heidegger aims to uncover the relationships underlying all individual meaningful references in everyday life.
"Being and Time" does not answer the question of the meaning of life, but rather engages with the meaning of meaning as related to existence. Heidegger's main question is therefore: "why is there anything at all rather than nothing?". According to Heidegger, Western philosophy has given different answers in its tradition as to what it understands by being, but it has never posed the question of being in such a way that it asked about the meaning of being. Heidegger criticizes previous philosophical understandings which described being as something individual. However, by just stating that something is, one cannot understand what something is. If one takes the hammer merely as an existing piece of wood and iron, its relation to the nail cannot gain meaning.
The Relation between Being and Time
For Heidegger, the failure of philosophical tradition to grasp existence is largely due to disregarding its relation to time. Being is not just something which is present but also something with a past and future. In "Being and Time" Heidegger tries to prove that time is an essential condition for an understanding of being, since it sets an horizon of understanding against which things can find meaning in relation to one another. For example, the hammer is used to drive nails into boards to build a house that will protect people from future storms. So it can only be understood in relation to people and in the context which makes the hammer more than just connected pieces of wood an iron.
The bottom line of Heidegger's "Being and Time"
is that thinking must be understood on the basis of new principles. There is a
need for a "fundamental ontology" to account for the question of
being and why thing are.