Difference Between Theory and Law

Main Difference – Theory vs  Law

Theory and law are two terms that we encounter in the field of sciences. Although theories and laws explain various concepts in science, there is a definitive difference between theory and law. Theory explains why something happens whereas law describes what happens when certain conditions are present. This is the key difference between theory and law.

This article explains,

1. What is a Theory
     – Definition, Characteristics, Examples

2. What is a Law
     – Definition, Characteristics, Examples

3. What is the difference between Theory and LawDifference Between Theory and Law - Comparison Summary

What is a Theory

Definitions of Theory

Theory is a set of verified explanations or statements about a phenomenon. The Oxford Dictionary defines theory as “a supposition or a system of ideas intended to explain something, especially one based on general principles independent of the thing to be explained”. The American heritage defines it as “A set of statements or principles devised to explain a group of facts or phenomena, especially one that has been repeatedly tested or is widely accepted and can be used to make predictions about natural phenomena”.

Characteristics and Examples

As the above definitions indicate, a theory is an explanation that is acquired through scientific methods. A theory is formed after constant observation and repeated experimentation. Einstein’s’ theory of relativity, Darwin’s theory of evolution, Lavoisier’s oxygen theory of combustion, quantum theory, Einstein’s theory of special relativity and cell theory are some examples of scientific theories.

The credibility of a theory depends on the amount of evidence that is used to support the theory. Some theories are revised or replaced by new evidence. For example, some new information such as DNA and genetics has been added to the cell theory which was originally formulated by Schleiden and Schwann.

Difference Between Theory and Law

Theory of Evolution

What is a Law

Definitions of Law

A scientific law is different from a theory. A law is a generalization that describes what happens when certain conditions are met. The Oxford dictionary defines law as “A statement of fact, deduced from observation, to the effect that a particular natural or scientific phenomenon always occurs if certain conditions are present”. The American heritage dictionary defines it as “A statement describing a relationship observed to be invariable between or among phenomena for all cases in which the specified conditions are met”.

Characteristics and Examples

As the above definitions explain, laws are typically based on observations, specially repeated experimental observations. To be more specific, it describes what happens when certain conditions are met. For example, Newton’s first law of motion states:

“An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.”

The condition in this law is written in italics. According to this law, the position of an object doesn’t change unless an external force is applied.

Some examples of scientific laws include Newton’s law of motion, Mendelian laws of heredity, and Boyle’s law.

Laws describe how something happens with proof, but they cannot explain why something happens. Laws are universally observable facts; therefore they cannot be challenged or revised.

Main Difference - Theory vs Law

Kepler’s law

Difference Between Theory and Law

Definition:

Theory: Theory is defined as a supposition or a system of ideas intended to explain something, especially one based on general principles independent of the thing to be explained.

Law: Law is defined as a statement of fact, deduced from observation, to the effect that a particular natural or scientific phenomenon always occurs if certain conditions are present.

Function

Theory: Theories explain the cause of a phenomenon.  

Law: Law describes the nature of a phenomenon.

Base

Theory: Theories are based on proof or evidence.

Law: Laws are based on scientific observations.

Conditions

Theory: Theories may not consist of conditions.

Law: Laws describe what happens when certain conditions are met.

Revision

Theory: Theories can be revised or replaced as new evidence comes to light.

Law: Laws are not typically revised since they are universally observable.

Image Courtesy:

“297234” (Public Domain) via Pixabay

“Kepler laws diagram” By Hankwang – Own work (CC BY 2.5) via Commons Wikimedia

About the Author: Hasa

Hasa has a BA degree in English, French and Translation studies. She is currently reading for a Masters degree in English. Her areas of interests include literature, language, linguistics and also food.