When is a Theory Really a Theory?

By Michael Edmonds 15/06/2011 5


A common complaint amongst scientists, particularly those who deal with creationists, is that the general public and media often misuse the word “theory”.

In science a theory arises when a hypothesis (or series of hypotheses) has been repeatedly tested and found to be a true description of the physical world. One example is the Kinetic Theory of Matter which specifies that the world around us is 1) Made of of tiny particles (atoms/molecules); 2) That these particles move relative to each other; 3) There are forces of attraction between particles. This theory was developed from, and verified by, many different observations of how matter behaves in the physical world.

However, I sometimes wonder if scientists themselves are too free with the use of the word “theory”. Over the last couple of years I’ve heard the terms “String Theory” and “the Multi-verse Theory” used quite a bit. Are there any physicists out there who can confirm whether or not theory is the correct term for these areas or would hypothesis or model be better terms? Are these terms used in physcis circles or just the media description of them?

And to all the scientists reading this, what do you consider to be theories in your area of expertise? Biology has the Theories of Evolution and Natural Selection, which are supported by mountains of observations, but what else?

In chemistry I would include:

The Kinetic Theory of Matter

Atomic Theory

Transition State Theory

Valence Shell Electron Repulsion Theory

Molecular Orbital Theory


5 Responses to “When is a Theory Really a Theory?”

  • Germ theory, Plate Tectonics, Quantum Theory, Heliocentric Theory, Cell Theory, Big Bang Theory, Intelligent Design – Just kidding.

    I would further refine your definition of a theory as the descriptive structure that ties together facts from multiple lines into a coherent whole that can be used to explain phenomena as well as predict facts that have yet to be discovered.

    It might be described as the underlying narrative of a discipline. But that might be giong a little far.

  • Darcy,

    Nice list, apart from the last one, ahem.

    Regarding Big Bang theory – how much evidential support is there for it? I’m not overly familiar with cosmology and physics.

    Alison, good points

  • Yeah, the Big Bang is one I got queried on after my own post on “theories” by science types that never-the-less have some idea that it’s somehow just a guess.

    I wrote a post around this a couple of years ago (back when I could curtail my verbosity), but the gist of it is the big bang acounts for (or predicts) the observed abundances of elements in the universe, predicted the cosmic microwave background radiation (both it’s existence and temperature), also predicts the composition of stars through cosmic history. That’s a start but the bottom line is that despite headlines of “The Big Bang shown to be wrong” (like Darwin was wrong) it’s pretty solid.