Biomedical Engineering Reference
In-Depth Information
Chapter 2
What is a Classification?
“Deus creavit, Linnaeus disposuit,” Latin for “God Creates, Linnaeus organizes.”
Carolus Linnaeus
CLASSIFICATIONS DRIVE DOWN THE COMPLEXITY
OF KNOWLEDGE DOMAINS
The human brain is constantly processing visual and other sensory informa-
tion collected from the environment. When we walk down the street, we see
images of concrete and asphalt and grass and other persons and birds and
so on. Every step we take conveys a new world of sensory input. How can
we process it all? The mathematician and philosopher Karl Pearson
(1857
1936) has likened the human mind to a “sorting machine” [11]. We
take a stream of sensory information and sort it into objects, and then
we collect the individual objects into general classes. The green stuff on
the ground is classified as “grass”, and the grass is subclassified under
some larger groups such as “plants”. Flat stretches of asphalt and concrete
may be classified under “road” and the road might be subclassified under
“man-made constructions”. If we did not have a culturally determined clas-
sification of objects in the world, we would have no languages, no ability to
communicate ideas, no way to remember what we see, and no way to draw
general inferences about anything at all. Simply put, without classification,
we would not be human.
Every culture has some particular way to impose a uniform way of
perceiving the environment. In English-speaking cultures, the term “hat”
denotes a universally recognized object. Hats may be composed of many
different types of materials, and they may vary greatly in size, weight, and
shape. Nonetheless, we can almost always identify a hat when we see one,
and we can distinguish a hat from all other types of objects. An object is not
classified as a hat simply because it shares a few structural similarities with
other hats. A hat is classified as a hat because it has a relationship to every
other hat, as an item of clothing that fits over the head. Likewise, all
biological classifications are built by relationships, not by similarities [12].
 
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