Scientific Theories, Laws and Criteria of Adequacy

A scientific theory is a system of explanations of aspects of the natural world whose parts should have been tested and verified in accordance with the scientific method, using accepted protocols of observation, measurement, and evaluation results. Where possible, theories are tested under controlled conditions in an experiment. Here are some examples:

* cell theory, (Biology)
* atomic theory, (Physics)
* Big Bang theory, (Physics)
* Plate tectonics, (Geology)

Are theories revised? YES. All the time. As new discoveries are made, the theory needs to be tweaked and revised. The reason is that theories have many different parts and the parts are put together by inferential conclusions.

The distinction between scientific theory & scientific law 

Scientific laws and scientific theories are produced from the scientific method through the formation and testing of hypotheses, in order to predict the natural world. Both are typically well-supported by observations and/or experimental evidence. Scientific laws are descriptive accounts of how nature will behave under certain conditions. Scientific theories are broader in scope, and give overarching explanations of how nature works and why it exhibits certain characteristics.

So, for example, Newton's Second Law, F = ma is a formula.

(It states that the acceleration of an object as produced by a force is directly proportional to the magnitude of the force, in the same direction as the force, and inversely proportional to the mass of the object).

This formula belongs in a body of theories known as Classical Mechanics. Classical mechanics, is a branch of Physics that describes the motion of macroscopic objects, from projectiles to parts of machinery, and astronomical objects, such as spacecraft, planets, stars and galaxies.

Whereas laws should obtain all the time, theories incorporate laws with the purpose of explaining more general phenomena. They both explain, but laws are simpler.

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We need good explanations. In order to achieve this, we need to create a criteria of adequacy. Here are five points:

● Simplicity → Quality of relying on only a small number of assumptions (less is more).
● Scope → The amount of diverse phenomena (more is more).
● Consistency/Coherence → Lack of contradictions. (especially internal contradictions)
● Fruitfulness → The number of new facts predicted or problems solved (ability to make predictions).
● Conservatism → Quality of fitting well with existing theories (previous conclusions).