Earlier in this century, many philosophers of science (for example,
Rudolf Carnap) drew a fairly sharp distinction between theory and
observation, between theoretical terms like 'mass' and 'electron', and
observation terms like 'measures three meters in length' and 'is _2°
Celsius'. By simply looking at our instruments we can ascertain what
numbers our measurements yield. Creatures like mass are different: we
determine mass by calculation; we never directly observe a mass. Nor an
electron: this term is introduced in order to explain what we observe.
This (once standard) distinction between theory and observation was
eventually found to be wanting. First, if the distinction holds, it is
difficult to see what can characterize the relationship between theory:
md observation. How can theoretical terms explain that which is itself
in no way theorized? The second point leads out of the first: are not
the instruments that provide us with observational material themselves
creatures of theory? Is it really possible to have an observation
language that is entirely barren of theory? The theory-Iadenness of
observation languages is now an accept- ed feature of the logic of
science. Many regard such dependence of observation on theory as a
virtue. If our instruments of observation do not derive their meaning
from theories, whence comes that meaning? Surely - in science - we have
nothing else but theories to tell us what to try to observe.