Discussion:

Audience:  Philosophers can explain what “beauty” in a final theory could be like.

James:  Really good art historians become physicists, not philosophers.

Audience:  Conceptual work can be contributed by philosophers.

James:  But who can do it when it’s coupled technically with the physics?

James is unclear what the role for philosophers is here.  There are good philosophers, and there are good physicists, but are there good philosopher-physicists out there?

limitations of the method:

– no guarantees

– progress is slow

– problems of interpretation

Two other approaches:  hydrodynamic and condensed matter.

James:  Intriguing ideas but not well-developed as yet.

Virtues of general method:

– it’s a *method* and not speculative ontology.

– it holds promise of making contact with other approaches

– self-correcting

– it’s worked in the past

Basic tenets of stochastic gravity:

– assume a complete micro theory incorporating gravity

– assume it’s a quantum system

It must be open.  (And a couple other characteristics that flew by me…)

One direction is “kinetic theory”…

James:  This is not a theory of quantum gravity.  This is a proposal for how to move towards a theory of quantum gravity in incremental steps.

Audience input:  This is not an attempt to define a fundamental theory.

James:  The incremental extensions may intersect other approaches at various points (condensed matter approach for instance).

Enter stochastic gravity:  add a term corresponding to a heat bath (?) to the semi-classical Einstein equation.  Use this term to probe the nature of further corrections.

Audience input:  The extra term represents quantum fluctuations of the stress-energy tensor.

Historical analogy:  progressive modifications of Maxwell’s theory by Lorentz and others that culminated with Einstein.  (Ptolemaic fine tinkering, as another example…)

A conservative extension of SCG.  In Virginia, you buy old houses, tear them down, and build new ones (apparently).

No theory of quantum gravity here; i.e., it’s not an end state.  (No membranes vibrating in various ways.)

Just a way of generating progressive modification of theories we have:  the “Lorentz strategy”.

The *real* issue with SCG is that we’ve thrown out all the interesting quantum stuff.

So what’s left?  Revolutionary stuff?  James says… “no”.  All we have to do is extend SCG by putting back in all the interesting quantum stuff.