Common Sense and Quantum Mechanics
Consider what happens when you observe a game of chess. You are working
with a partition of the world into that, in the region of the chessboard,
which you are focusing on, and that which is ignored. Your focus brings
with it a certain granularityyou are interested, not in the atoms or molecules
within the board and its pieces, but rather only in the board and pieces
themselves. Moreover, you are interested in the latter not as constituting
a mere list, or set, but rather as they exist within a certain arrangement.
The board as you perceive it is divided into cells (squares). In some of
these cells pieces of specific kinds are located.
To understand what is going
on here, we need to understand the notion of partition and the associated
notion of cell. Partitions have built-in granularity. (Consider a map of
France depicting its 91 départements or its 311 arrondissements.)
A partition is the result of applying a certain coarse- or fine-grained
grid of cells—the minimal units of the partition—to a certain portion of
reality.
For a partition to do its
work, it needs to have cells large enough to contain the objects that are
of interest in the portion of reality which concerns the judging subject,
but at the same time these cells must somehow serve to factor out the details
which are of no concern. A partition, as here conceived, is accordingly
a device for focusing upon what is salient and also for ignoring or masking
what is not salient. We can think of it as being laid like a net over whatever
is the relevant object-domain, and, like a net (or a latticed window of
the type employed in Alberti's reticular painting grid), it is to a large
degree transparent. Thus, importantly, it does not in any way change the
reality to which it is applied.
Partitions are at work whenever
we have any sort of cognitive experience of the empirical world. They are
at work not only in our common-sense experience, but in all theorizing,
classifying, mapping, tracking and data-gathering. The new ‘consistent
histories' interpretation of quantum mechanics advanced by Griffiths, Gell-Man,
Omnès and others, shows how the notion of partition can be used
as the basis for an understanding of quantum phenomena. The talk will provide
an introduction to the theory of partitions, and show how it can be applied
to provide an interpretation of quantum mechanics that is compatible with
common sense.