Here is some discussion from the blog:
"Even though we have lost yardsticks by which to measure, and rules under which to subsume the particular, a being whose essence is a beginning may have enough of origin within himself to understand without preconceived categories and to judge without the set of customary rules which is morality."
--Hannah Arendt, “Understanding and Politics”
Arendt here is speaking of understanding and judging by oneself – without reliance on “preconceived categories.” This is what she meant by “thinking without a banister.” As did Nietzsche—who asked in Thus Spoke Zarathustra, "Have not all hand-rails [banisters] and foot-bridges fallen into the water?” Arendt saw the loss of yardsticks and measures that mark our age as both a crisis and an opportunity.
When one thinks without a banister, one thinks without reference to either unquestioned categories of thought or to unquestionable ones.
As Martin Luther King, Jr. said, "bombs that are dropped abroad explode at home."
(1) - http://www.hannaharendtcenter.org/?p=1406
(2) - http://brattononline.com/