I suppose the honest answer for wanting linguistics (or semiotics) to
subsume activity is just laziness... if I can treat something as part of
language, or alternatively as a kind of language, I know how to work as a
linguist or semiotician on it... or if language has already evolved a good
representation of activity and I have a model of language, then the job's
done... probably the Hjelmslev in me... too imperialistic.
More seriously, as a functional linguist I'm ecologically interested in
the relation of lnaguage to its context, including other semiotic systems
and other than semiosis - it's relation to the rest of the discursive and
non-discursive spheres. On one reading of the message I'm responding to,
you seem to be subsuming the 'material' into semiosis, or at least the
material that matters into semiosis? Yes?
Jim Martin