13 Inductive vs. Deductive Reasoning
Deductive reasoning, also known more briefly as “logic,” is the process for
which facts can be deduced from other facts in a completely unambiguous
manner using axioms and rules. Modern digital computer programs are
fundamentally logical. They function in a manner that is unambiguously
deterministic.
Reality is unlike a computer in many respects. It is much larger and far
more complex than any computer program could ever be. Furthermore, most
of what takes place is governed by rules that are either unknown or only
imperfectly known. The lack of full knowledge about reality manifests itself
as ambiguity and nondeterminism. There is no reason to suppose that reality
is actually ambiguous or nondeterministic. Despite this situation, people
manage to function effectively in the world.
There are two important mechanisms that people use to function in the
world. The first is the ability to restrict attention to a small part of all of
reality. The second is to accept that information is uncertain. These two
mechanisms are related to one another. In theory, if one were capable of
omniscience, then reality would be as unambiguous and deterministic as a
computer program. However, since people are not capable of such a capac-
ity, we are forced to suppress nearly all of what occurs in the world. The
suppressed details manifest themselves in the form of uncertainties, ambi-
guities, and nondeterminism in the details that we do choose to observe.
The former mechanism is called by various names such as “abstraction” and
“relevance.” Ontologies are fundamental to specifying what is relevant. The
latter mechanism is fundamental to scientific reasoning. The combination of
these two mechanisms is the subject of this part of the book.
When scientific reasoning is relatively simple, it is easy to ignore the role
of the ontology, leaving it informal or implicit. However, medicine and bi-
