In 1927 Martin Heidegger published Being and Time. His purpose is to offer a new account of understanding, the interpretative one, making it the central mode of human existence (or Dasein) to cause a revolutionary break from the traditional philosophical emphasis on problems about knowledge and on the dichotomy between subjectivity and objectivity.
Before Heidegger, hermeneutics is merely one branch of philosophy that analyses the phenomenon of understanding in contrast to other human activities such as knowledge or language. Understanding here is the ability to offer interpretations in contrast with an objective knowledge. Pre-Heideggerian hermeneutics distinguishes humanistic understanding and interpretation from the lawlike explanations of the natural science. Hermeneutics, not giving causal explanations, appears to be at best only one possible interpretation of human experience (Geistswissenschaft , see Dilthey and his attempt to claim a separate status to it as example of a distinct cognitive operation, the understanding. According to Heidegger, the weakness in this tradition is that it leaves understanding as a derivative and deficient subspecies of knowledge plagued by the threat of relativism.
HeideggerUs solution is to make "understanding" the defining feature of existence. All other cognitive acts become derivatives of this general understanding. This understanding is the only way we can relate to our world. As Hoy explains, it is "our most basic ability to live in and cope skillfully" with our ever-changing world. (p.173)
Once understanding becomes the central feature of human existence, the conception of subject/object is abolished, and the hermeneutic circle is extended all the way down to existence. His turn shows that the subject-object model is not the only possible starting point for philosophy, but instead it derives from the more basic starting point where Dasein and the world are coterminous in understanding. Heidegger conceives of Dasein and world as forming a circle, and he thus extends the traditional hermeneutics circle between text and its reading down to the most primordial level of human existence. (see sections 31 and 32 of Being and Time)
Since (interpretive) understanding is the only relation of Dasein to the world, understanding becomes the central phenomenon for philosophy. Instead of being one among many branches of philosophy, hermeneutics comes to be its defining feature.
Other useful stuff:
Understanding : distinctions
Our fundamental understanding consists both of automatic interpretation of mundane objects and activities (Auslegung ), and of reflective interpretation of the philosophical sort (Interpretierung ). All cognitive activity, however, (including philosophy) is grounded in the basic understanding of our Dasein. Thus, Heidegger eschews the problem of traditional hermeneutics which questions the connection of subject and interpretation by making RunderstandingS their common denominator.
An understanding of the context involves an appreciation of its range of possibilities; that is, what it makes sense to do in a particular situation. This is not dependent on delineating all known things (facticity), but on a holistic grasp of the situation and DaseinUs role in it (factuality). Understanding, then, is not a mere collection of discovered facts (Entdecktheit). Instead, it is the disclosure (Erschlossenheit ) of context behind these facts, a context which makes the facts intelligible.
Interpretation pp. 181-187, to define the basis on which hermeneutics is founded and has moved from After Heidegger pp. 188-193 to know something more about contemporary continental Philosophy
from David Couzens Hoy, Heidegger and the hermeneutic turn, Cambridge
University Press, Cambridge 1993, pp. 170-194