The Impact of Aristotelian Thinking on Information Retrieval
Steve Halladay
ABSTRACT
Many consider Aristotle, along with Plato, to be the greatest western philosophers. Aristotelian
thinking has had far reaching effects that influence today’s science and technology. This paper
considers these influences and describes how Aristotelian thinking has enabled the creation of
technologies including those used for Information Retrieval. At the same time, the broad
application of Aristotelian thinking is also fundamentally limiting the technology’s capabilities.
Exploring the effects of these philosophical forces on Information Technology may help
researchers to create even more powerful systems.
INTRODUCTION
Aristotle was one of history’s foremost philosophers who left a legacy that continues to affect
each of our daily lives. His appreciation for the role of empirical observation sets him apart as
one of the framers of today’s scientific method. Although he lived over 2300 years ago, we still
see the effects of his work in our modern sciences.
One example of an Aristotelian contribution is in the area of ontological taxonomies for knowledge
representation. Aristotle’s notion was that he could classify everything within a taxonomical
hierarchy. The implications of this classification are twofold; first, there is a relationship between
all things that can be described by a hierarchy, and second, once similar things are grouped into
a class, they may be treated in a similar way. The latter point is illustrated in Aristotle’s famous
syllogism: Socrates is a man. All men are mortal. Therefore, Socrates is mortal.
In spite of Aristotle’s wonderful intellectual contributions, some of Aristotle’s thinking led him to
inaccurate conclusions. For example, while Aristotle was aware that the earth was round, a
concept that was generally ahead of it’s time; he was also under the misconception that the earth
was the center of the universe. Another well known fallacy that captured Aristotle was the belief
that objects of differing mass fall at different rates. This latter misconception is rather surprising
given Aristotle’s penchant for observation.
The point of this discussion is that while Aristotle made some amazing intellectual contributions,
he was human and fallible. Therefore, we should think critically about the path we are on; a path
initiated by Aristotle. We should appreciate the strengths and weaknesses of our thought
processes as well as the useful and hindering applications of these processes.
EFFECTS OF SIMPLIFICATION
The result of Aristotle’s classification was the use of simplification or abstraction to help people
deal with otherwise unwieldy systems. For example, all animals of the class cow can be milked,
all animals of the class bird can fly, and all animals of the class fish can swim. Therefore, when
someone describes an animal as a cow, bird or fish, we can have certain understandings of the
animal’s capabilities and expectations about how we might interact with the animal.
Initially classification mechanisms simplified thought and communications. This simplification
occurs because classification alleviates the need to describe all objects’ attributes. If an object is
identified with a class, then, by definition, the object has the attributes associated with that class.
The use of classification concepts yielded some very concrete results during the industrial
revolution. The advent of mass production was an extension of the concept of classification.
Products were manufactured from classes of objects with attributes so similar, the objects
became interchangeable. For example, Henry Ford mass produced cars in such a way that any
Model A engine would fit into any Model A chassis. In fact, the more similar the objects of a
class, the better the manufacturing process works.
The idea of creating manufacturing objects with high degrees of similarity eventually led to the
notion of specification. A specification is really a detailed description of the objects that are
considered to be in the same classification or set. All objects that “meet specification” are
considered to be valid members of the set and are therefore perfectly acceptable to the
manufacturing process.
The concept of specification has a related supporting concept called tolerance. Tolerance refers
to the amount of acceptable variation of attributes within the set. As tolerance becomes “tight”
the degree of acceptable variation diminishes. Tight tolerance decreases the degree of variability
within the manufacturing process and can reduce the costs of the manufacturing process.
However, creating objects with tight tolerance may increase the costs of producing the object.
Many of the manufacturing enhancement processes, as introduced by Deming for example, focus
on tightening tolerance to reduce variability within the manufacturing process.
The benefits of classification are not limited to the industrial revolution. The computer industry
employs the concepts of classification, specification and tolerance to create intellectual objects
that are similar, or have the same expected behavior. In the domain of computer science these
objects, embodied as software, may appear very different but have a behavior that meets a
specification. Software designs that employ these concepts are robust because they can be
extended by creating additional objects within the set of the specification which may have
increased capability. For example, an object that performs a computationally intensive
calculation may be replaced by an object of the same class that allows the calculation to be
performed on a remote, higher speed processor.
The significant point of this section is that classification helps us to simplify our world conceptually
which enables significant technological advances.
EFFECTS OF CLASSIFICATION
Albert Einstein is quoted a saying “Things should be made as simple as possible – but no
simpler.”
Sometimes there is too much of a good thing. This may be the case with respect to the
simplifying effects of classification. It is understandable to think that since the notions of
classification have served us so well; the answer to all our problems is to increase the use of
classification. This is specifically what many conventional information retrieval systems do.
Many conventional information retrieval systems start by creating a hierarchical classification of
concepts of interest. Next, these systems identify which words indicate the membership in
specific sets within the hierarchy. By using these words, the retrieval systems assign documents
to different sets within the hierarch. Requests for information are handled in a similar manner by
using the words in the request to determine the set of interest within the hierarchy. Once the
system identifies the set of interest, retrieval is a simple matter of returning all documents within
the set.
However, information retrieval systems have been plagued for many years with precision/recall
tradeoff problems. It seems that these systems can either retrieve all the relevant documents
with along with many non-relevant documents (i.e., high recall, low precision), or these systems
can retrieve a few, but not all, documents that are mostly relevant (i.e., high precision, low recall).
But these systems have not yet been able to retrieve only the relevant documents.
For those steeped in Aristotelian thought patterns, the natural solution seems to be to create
more classification sets, more levels in the hierarchy and identify more attributes to distinguish
between documents. This approach is bound to yield some pay-offs, but the creation of the sets
is laborious and time consuming. As a result, trying to solve this problem using augmented
classification will eventually yield diminishing returns.
An alternative perspective to consider is that classification is part of the problem instead of the
solution. As the information revolution matures, the simplifying Aristotelian mechanisms may
actually be masking many of the intricate relationships necessary for higher quality retrieval. In
order to support the theory that classification mechanisms are actually inhibiting information
retrieval, we must explain how this is possible.
First, one might consider the effects of set boundaries. Those of us with a mathematical and
scientific background are so familiar with sets that we accept sets as a fact of life. We view the
world in such a way that objects are either members of a set or they are not. But closer
examination can challenge our perspective.
For example, consider the set of all chairs. Chairs are in the set and tables are not. What is a
chair? Chairs have four legs, a seat and a back. What about objects with four legs and a seat but
no back? We refer to these as stools. Are stools in the class of chairs? Similarly, what about
objects with three legs a seat and a back? Are these objects still chairs? Perhaps an even more
difficult judgment might be to consider a rock in a forest upon which one chooses to sit. Is such
an object considered a chair? And so it is that as we challenge various combinations of attributes
that define the set, we find that it is not always clear where the set boundaries lie. If determining
the classification for a concrete object like a chair is ambiguous, one can only imagine how much
more ambiguous the classification of non-concrete objects, like text, might be.
Another concern with regards to classifying text is determining which part of the text to classify.
For example, a paper such as this might have several sections. Each section discusses a
different topic. Each section consists of multiple paragraphs that, in turn have unique topics and
differing levels of conceptual abstraction. Carried further, each paragraph has several sentences
and each sentence may have multiple phases, each expressing a different concept. Now, in
order to correctly classify the document, one must decide if the document should be represented
as a single point within a classification set or sets, or as multiple points within multiple sets.
Either choice will have detrimental affects of both precision and recall.
Finally consider the classical taxonomy which consists of a hierarchy. Hierarchies are essentially
sets of sets. Humans have an affinity to taxonomies because taxonomies seem to have a
specific place for everything. To find an object within a hierarchy, one only need start at the root
and make successive branching choices until one arrives at the desired object location. The
problem with hierarchies is that they are only as helpful as one weakest choice. When moving
from ht root of the hierarch to its leaves, it only requires one poor judgment to get on the wrong
branch and not find the desired object. For this exact reason, hierarchies do not scale well. In
order to increase the capacity of a hierarchy, one must increase the breadth or depth of the
hierarchy. Increasing the breadth makes each decision more difficult and, therefore, more errorprone. Likewise, increasing a hierarchy’s depth will increase the number of decisions that must
be made in order to find the desired object and thereby increase the opportunity for error. Viewed
in this light, the application of hierarchies in information retrieval is like creating a shell game of
shell games.
CONCLUSIONS
Considering the effects of simplification as well as the affects of classification, one is left
wondering if the information retrieval industry is doomed to languish in the doldrums somewhere
between precision and recall. This assessment is correct only if information retrieval researchers
choose to continue to think the same way they have to this point.
Aristotle was a great thinker. Aristotle had some thoughts that were very helpful and some that
were not. But perhaps the greatest aspect of Aristotle’s thinking lies not in the resulting thoughts
themselves, but more importantly in the thinking process he employed. Aristotle had a knack for
critical thinking. He observed phenomena and then constructed conceptual models that were
consistent with his observations. These models had an honest conceptual integrity that was often
independent of social pressures of preconditioning. If information researchers are to move
forward, perhaps the most fertile results will occur not by thinking Aristotle’s thoughts, but by
thinking more like Aristotle.