Theoretical Definition - Examples

Examples

Theoretical definitions are common in scientific contexts, where theories tend to be more precisely defined, and results are more widely accepted as correct. The definitions of substances as various configurations of atoms are theoretical definitions, as are definitions of colors as specific wavelengths of reflected light. In such cases one definition of a term is unlikely to contradict another definition based on a different theory. However, in areas such as philosophy and the social sciences, theoretical definitions of the same term often contradict each other depending on whose theory is being used as the basis.

Another example of a theoretical definition: the length of a metre is "the distance traveled by light in a vacuum during a time interval of 1/299,792,458 of a second". This is based on the first postulate of special relativity theory that the speed of light in vacuum is the same to all inertial observers (i.e. it is a constant, and therefore a good measure of length). Thus we have defined 'metre' according to other ideas contained in modern scientific theory. Rejection of the theory underlying a theoretical definition leaves the definition invalid for use in argument with those who reject it — neither side will advance its position by using terms the others do not accept.

For example, John Searle's Chinese room thought experiment illustrates how differing theoretical definitions of "thinking" have caused conflict amongst artificial intelligence philosophers. Some philosophers might call "thought" merely "having the ability to convince another person that you can think". An accompanying operational definition for this theoretical definition could be a simple conversation test (e.g. Turing test). In contrast, Searle believes that better theoretical and operational definitions are required.

A recent effect of differing theoretical definitions occurred when millions of Americans went from normal to overweight in a day's time. The change in the theoretical definition of "overweight" was based on new theories put forth by the National Institutes of Health suggesting greater risks than originally believed. The government then changed the operational definition of "overweight" to "having a BMI over 25" (rather than 27 for women and 28 for men). Changing our understanding of when someone is "overweight" put several million more in that category, even though they had not actually gained or lost any weight.