 

                          FACTS AND THEORIES

            The path that leads from observation to theory so
       commonly ends in speculation so absurd that we enter upon it
       only with reluctance.  But whatever reservations we may have
       about the application of physical theory to biologic
       phenomena, we cannot do without it.  To attempt to diagnose
       and treat glaucoma without considering the physics of
       pressure and flow is like trying to correct ametropias
       without regard to the physics of image formation by lenses.
       All theories are approximations to experience, some are more
       useful, others, less.  No theory is ever so valid that it
       cannot be misapplied, and the correct application of a
       theory vies in difficulty and importance with its
       elaboration in the first place.

            No obstacle to valid application of theory is greater
       than exaggeration of its consequences, the implicit claims
       of possession and control that it entails.  One assumes,
       erroneously, that there are a "causes", and that theory can
       capture them, that to know the causes is to control the
       thing.  An established theory, moreover, may be so
       compelling as to preempt truth, foreclose further thought,
       and cast the mind into the role of a servile mimic.
       Etymology suggests what theory is: a way of looking at
       experience, and as such, a personal, subjective enterprise.
       Each one must undertake it for himself.  Objective theory,
       shared theory, theory as the function of community, like
       shared vision, is an anomaly, the subject of a chapter in
       the philosophy of mathematics that remains to be written.
       Just as no one bartender can drink for you, no seer can see
       for you and no professor can think for you.  Everything that
       matters you must do for yourself.  When you are confronted
       with someone elses theory, my advice is that you take the
       theory apart, see how it works, find out whence it comes,
       what it presupposes, and what it entails, and what its
       purveyor has to gain by peddling it.  Invalid theory will
       dissipate in the face of such scrutiny and will no longer
       hinder your thought.  But if the theory is good, then by so
       testing it you will have made it your own.

            The history of medicine is replete with illustrations
       of the limitations of theory.  Indeed, the rejection of
       cosmological speculation and the insistence on clinical
       observation were at the foundations of Hippocratic medicine.
       According to the Hippocratic school, thought which begins
       not from a clear impression, i.e. observation, but from a
       plausible fiction, i.e. a mathematical model, leads action
       into a "blind alley" and causes the physician to harm rather
       than to help his patient.  But in the intervening centuries
       we have learned that observation cannot be divorced from
       theory; as a German author once put it: "Das Hoechste waere zu
       begreifen, dass alles Faktische schon Theorie ist."  (The
       ultimate insight is to understand that "facts" *are*
       theories.)  The escape from theory to facts is an illusion.
       On the contrary, from the uncounted profusion of facts
       accessible to us, we select those that are most
       "meaningful", i.e. those that have the maximum of
       theoretical significance, and the ability to recognize the
       significance of observations, of facts, is, after all, what
       distinguishes the scientist from the laboratory technician.
       These considerations are an apposite introduction to
       observation of the optic disc, because this structure, as I
       shall show, is a most felicitous bridge between observation
       and theory, more so than any other anatomic structure of the
       eye that I can think of.

            The disc is visible to each one of us with his/her
       ophthalmoscope.  I dwell on this obvious fact not to
       disparage more recondite techniques of study.  But by the
       time the tissue has been cut and fixed and mounted and
       sectioned and photographed, it is no longer accessible to me
       for my own observation.  I must believe what I am told, and
       I am constrained to draw conclusions from photographs that I
       had no occasion to take or to select.  I have no alternative
       then but to suspend my judgment and to believe, or
       disbelieve what I am told.  Judgment then becomes an
       exercise in scholarship, in evaluating, comparing and
       drawing conclusions from the reports of others.  Whatever
       value such scholarship may have, it is not nearly so
       satisfying as looking through my own ophthalmoscope to see
       and to judge for myself.


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Copyright 2006, Ernst Jochen Meyer
