... that invisible, translucent yet changeable medium through which we looked ...

In front of my eyes, in front of Albertine's, there had been not just the morning sunshine but that invisible, translucent yet changeable medium through which we looked, I at her actions, she at the importance of her own life: that is to say, those beliefs which we do not perceive but which are no more a pure vacuum than the air we breathe; they compose around us a changing atmosphere, sometimes excellent, often unbreathable, which we could usefully measure and note as carefully as the temperature, pressure and season, for each of our days has its individual character, physical and psychological.

quoted in:
Proust, Marcel
"The Prisoner" (In Search Of Lost Time, Volume 5)
p. 133, Penguin Classics, 2003

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By far the finest literary exposition of the concept of Weltanschauung
(http://en.wikipedia.org/wiki/Weltanschauung) (http://www.fordham.edu/halsall/mod/1918freud-civwelt.html)
that I have ever read - and written maybe seventy years before used by Peter Checkland in his Soft Systems Methodology work
(http://en.wikipedia.org/wiki/Peter_Checkland) (http://en.wikipedia.org/wiki/Soft_systems) (http://www.brunel.ac.uk/~bustcfj/bola/research/ssm.html) (http://members.tripod.com/SSM_Delphi/ssm4.html) (http://valinor.ca/ssm3.html).

Here, Proust vividly describes the essential invisibility yet pervasiveness that constitutes a "Weltanschuung" that guides our thoughts (shallow and deep). Yet not only inform our thinking, but, by means of an almost self-referential loop, constitutes the bedrock by which thinking itself can only occur (in the same manner that air itself constitutes the means whereby (human) life can exist).