Single theory in the natural sciences

Question

I understand why in natural sciences multiple theories are required to have a better understanding of the natural world. Such as in physics to understand schrodingers wave function we need wave mechanics as well as quantum mechanics. Similarly to understand global warming you need the resonance theory of particles in physics and the chemical reaction of ozone depletion in chemistry to have a better understanding on how the natural phenomena works better.

My question however is, what will be an example where multiple theories are not required in the natural sciences?

Like what may be an argument supporting why one theory alone in the natural sciences may be better to understand a particular aspect of the natural world, than multiple theories used to understand that same particular aspect of the natural world ?

Could anyone give me some insights to this? Thank you

Answer 1

The natural world is a complicated place. I've never heard of any reasonable scientist or philosopher of science claim only one theory is needed to understand a phenomenon. Theories, like words in a paragraph, support each other in order to function.

Some scientific theories are more important than others, such as the theories of relativity, quantum theory, the theory of the cell, and evolutionary theory, but the external universe (as opposed to our understanding of it) is a large, complicated place, and no one theory could possibly explain, predict, and describe nature.

Now, that being said, sometimes multiple theories are REPLACED by a single theory. This is known as theory reductionism. A classical example of that is the division between organic and inorganic chemistries, where were presumed to be different sciences since organic compounds were presumed to have a vital force which animated them and gave them biological properties. Currently, it is understood that organic and inorganic compounds are both subject to the same general rules which govern atoms in the periodic table. Another example of two theories would be Galileo's work on bodies on earth and Kepler's work on orbits which were shown to be equivalent roughly under Newtonian mechanics (which were then later shown to be a special case of relativistic physics).

In these cases, sometimes two theories which appear to show different phenomena are really two differing aspects of the same phenomenon.

Two modern philosophical theories which address at a metaphysical level the relationship between our theories and the external world are transcendental idealism and philosophical realism, the former claiming the external world is relatively unknowable, and the latter disagreeing heartily on many points, except that naive realism is an untenable philosophical position.

Answer 2

Theories are only explanations of what we observe, and how to predict future actions. They are not explanations of the 'thing' in itself. D'Arcy Wentworth Thompson says in his book On Growth and Form (p 288):

For as Newton said, to tell us that a thing "is endowed with an occult specific quality, By which it acts and produces manifest effects, is to tell us nothing; but to derive two or three general principles of motion [author's footnote] from phenomena would be a very great step in philosophy, though the causes of those principles were not yet discovered."

Footnote: This is the old philosophic axiom writ large; Ignorato motu, ignoratur natura, which again is but an adaption of Aristotle phrase [Greek] as equivalent to the "Efficient Cause". Fitzgerald holds that "all explanations consist in a description of underlying motions" (Scientific Writings, 1902, p 385); and Oliver Lodge remarked, "You can move Matter; it is the only thing you can do to it."

Although we may in time reduce the number of theories, or find a better explanation or theory to describe interactions of matter and forces, no physical theories are absolute as none solve the question of the "Efficient Cause". The 'Efficient Cause' is the realm of philosophy not scientific theory.