Theory
Table of Contents
(from Theories of AI pg. 4) In a field of science or engineering, a “theory” usually refers to a system of concepts and statements on the subject matter of the field. Generally speaking, there are two types of theory:
1. Descriptive theory
Such a theory starts with certain observations in the field. The theory provides a generalization and explanation of the observations, as well as predictions for future events, so as to guide people’s behaviors. The theories in natural science are the best examples of this type.
e.g. Physics
2. Normative theory
Such a theory starts with certain assumptions, then derives conclusions from them. When the assumptions are accepted as applicable in a field, all the conclusions should also be accepted as true. Mathematics and engineering theories are the best examples of this type.a
e.g. Maths
3. A theory is either Descriptive or Normative
Though it is possible for these two types of theory to interweave (in the sense that parts of a theory may belong to the other type), for a theory as a whole its type is still usually clear.
For example, modern physics uses a lot of mathematics in it, but it does not change the overall descriptive nature of the theories in physics.
On the contrary, computer science is mainly based on normative theories on how to build and use computer systems, even though empirical methods are widely used to test the systems.
