The world can only be grasped by action, not by contemplation† The hand is the cutting edge of the mind.

-Bronowski,Jacob
  The Ascent of Man, ch.3.

Soit donc que vous composiez, soit donc que vous jouiez, ne pensez non plus au spectateur que s'il n'existait pas. Imaginez sur le bord du the¤  a"  tre, un grand mur qui vous se¤  pare du parterre; jouez comme si la toile ne se levait pas. Whether you compose or act, think no more of the spectator than if he did not exist. Imagine at the edge of the stage a large wall which separates you from the orchestra; act as if the curtain never rose.

-Diderot, Denis
  Discours sur la poe¤  sie dramatique, introducing the theatrical concept of the'fourth wall'.

   We stand today on the edge of a new frontier. But the new frontierof which I speak isnot a set of promises.It is a set of challenges. It sums up not what I intend to offer the American people, but what I intend to ask of them. It appeals to their pride, not their pocketbooköit holds out the promise of more sacrifice instead of more security.

-Kennedy,John F(itzgerald)
  On accepting the Democratic Convention's presidential nomination,15  Jul.

As a military man who has given half a century of active service,Isay inall sincerity thatthenucleararmsracehas no military purpose. Wars cannot be fought with nuclear weapons; their existence onlyadds to our perils because of the illusions that they have generated. The world now stands on the brink of the final abyss. Let us all resolve to take all possible practicable steps to ensurethat we donot, through ourownfolly, go over the edge.

-Nicholas, 1st Earl
  Speech at the Council of Europe in Strasbourg,11 May.

The politician is trained in the art of inexactitude. His words tend to be blunt or rounded, because if they have a cutting edge they may later return to wound him.

-Murrow, Edward (Edgar) R(oscoe)
Attributed.

A touch of science, even bogus science, gives an edgeto the superstitious tale.

-Pritchett, Sir V(ictor) S(awdon)
  The Living Novel,'An Irish Ghost'.

   To know that light falls and fills, often without our knowing, As an opaque vase fills to the brim from quick pouring, Fills and trembles at the edge yet does not flow over, Still holding and feeding the stem of the contained flower.

-Rogers,Will
  The Lost Son,'The Shape of Fire'.

It's the little questions from women about tappets that finally push men over the edge.

-Roth, Philip Milton
  Letting Go, pt.1, ch.1.

Anyway,I keep picturing all these little kids playing some game in this big field of rye and all. Thousands of little kids, and nobody's aroundönobody big, I meanö except me. And I'm standing on the edge of some crazy cliff.What I have to do, I have to catch everybody if they start to go over the clifföI mean if they're running and they don't look where they're going I have to come out from somewhere and catch them. That's all I'd do all day. I'd just be the catcher in the rye and all. I know it's crazy, but that's the only thing I'd really like to be.

-Salinger,J(erome) D(avid)
The Catcher in the Rye, ch.22.

The artist, like the idiot or clown, sits on the edge of the world, and a push may send him over it.

-Sitwell, Sir (Francis) Osbert
  The ScarletTree, bk.4, ch.2.

Never being, but always at the edge of Being.

-Spender, Sir Stephen Harold
  'Never Being'.