Information Technology Reference
In-Depth Information
to traditional methodological approaches that rely on precisionism. Consider, for
example, the following description of pneumococcal lobar pneumonia:
“In adolescents and adults the onset is sudden and may come 'out of the
blue'; but often the patient has a cold or other upper respiratory infection
and rapidly becomes much more ill, perhaps with an initial rigor but always
with a sharp rise in temperature, usually to 101-103 F. Pleuritic pain usu-
ally develops over the affected lobe. The patient may become aware that
he is breathing rapidly and certainly feels ill. Initially there may be a dry,
painful cough but soon the cough becomes productive of sputum which is
characteristically 'rusty' due to its content of altered blood from the foci of
red hepatization; quite commonly, however, it is purulent or slightly blood-
stained. It is often viscid and difficult to expectorate and this adds to the
patient's pain” ([6], p. 18.28).
This passage from a standard medical textbook exemplifies the usual medical lan-
guage and knowledge. Replete with vague, natural language terms such as
adoles-
cent, adult, sudden, often, cold, rapidly, ill, much more ill, perhaps, rigor, usually
and so on, it conspicuously demonstrates that medicine is not mathematical physics
or mathematical biology. It is an inexact action field because, first, the language and
knowledge of the subjects constituting this field, i.e. the health care personnel and the
patient, are vague and uncertain; and second, their goals and decisions based upon
that language and knowledge are vague and uncertain as well. Fuzzy logic has en-
abled us to view this ubiquitous vagueness and uncertainty in medicine as an unavoid-
able consequence of the complexity and continuity of the 'real world out there', and
to learn how to cope with it. Seen from this new perspective, the patient as the subject
of medical language, knowledge, goals, and decisions appears as a highly complex
bio-psycho-moral system that is primarily governed by continuous variables. Thanks
to Zadeh's
incompatibility principle
([11], p. 28), we have learned to realize that it
is neither possible nor necessary to make precise every medical term and decision,
and thereby awkwardly make discrete the given continuum. On the contrary, Zadeh's
principle suggests that it is even desirable to fuzzify it, since significance is highly
desired in medicine. This task is easily attainable in the following way.
The denotation of a medical term is a class
X
of any objects or processes. The
Zadeh
fuzzifiability principle
which says that:
Any crisp theory can be fuzzified by replacing the concept of a set in that
theory by the concept of a fuzzy set ([12], p. 192; [13], p. 816; [13], p. 3)
will always enable us to reconstruct and treat the class
X
as a fuzzy set. It will thus
be correct and advantageous to postulate that:
Everything in medicine is fuzzy
rendering the entire medicine an application domain of fuzzy logic. Thus, about 2370
years after medicine's constitution as a discipline and profession by Hippocrates, it
has eventually received a methodology. All logical, methodological, and epistemo-
logical problems associated with medical vagueness now appear tractable ([8]).
