Relate Pinter's words in his Nobel acceptance speech on the elusive nature of truth in drama to the themes of external reality, identity and time in Landscape and Silence by Pinter and Endgame by Beckett.
I have corrected your question slightly as you referred to Endgame as being by Pinter while it was actually written by Beckett. I left it in the question, however, as there are obvious similarities and influences in common between the two playwrights' dramatic production.
Pinter's Nobel Prize Acceptance Speech (2005), a controversial lecture that sparked controversy for the writer's critical stance against the American-led war against Iraq, begins as follows:
In 1958 I wrote the following:
'There are no hard distinctions between what is real and what is unreal, nor between what is true and what is false. A thing is not necessarily either true or false; it can be both true and false.'
I believe that these assertions still make sense and do still apply to the exploration of reality through art. So as a writer I stand by them but as a citizen I cannot. As a citizen I must ask: What is true? What is false?
Truth in drama is forever elusive. You never quite find it but the search for it is compulsive. The search is clearly what drives the endeavour. The search is your task.
Although Pinter does not relate these words directly to the plays you have mentioned, the characters in those oeuvres do offer such radically different points of view on their existence that the viewers are forced to ask themselves which one, if any, is the real and true point of view on reality. You can read the three plays as calling attention to their form and self-reflexively wonder about the creation of a particular form of reality on the stage. The lack of communication between the characters in the play and their differing views on events and their lives constitute different forms of reality which invite audiences to problematize the objectivity of external events. They are asked to investigate the different forms of reality and critically evaluate them. In the worlds of Landscape, Silence and Endgame, each character creates his/her own reality, identity and time, a creative process that comes close to that of the playwright while writing for the stage.
Contrary to the elusive, yet compulsive, search for truth in drama, political language simply struggles to maintain and legitimize power. It is to make this point that Pinter refers to the Iraq conflict, revealing the fictitious assumptions under which it was approved and fought. Pinter concludes his lecture by claiming that the search for truth in the face of political power is "a crucial obligation" to restore the "dignity of man".