Theories: What Makes a Theory Scientific?

What makes a theory scientific ? 
– James J. Pearce, PhD 

• 1. Reason (or Rationality): 

Coherence – Claims made within the context of a scientific theory must be mutually consistent. Contradictory claims cannot both be true. Inferences about non-observable entities must adhere to the rules of a logic, but (as in the case of Quantum Mechanics) not necessarily a traditional logic. 

• 2. Naturalism: 

a. Intelligibility – It is assumed that all aspects of the universe are understandable in principle, and can be explained in terms of the same general principles which govern all natural behavior. Appeals to “mystery” or “the limits of human comprehension” are inherently irrational and unscientific. Appeals to the “mystical” or “supernatural” are excluded as a matter of principle. 

b. Empiricism – Only the evidence of the senses carries decisive weight. Whatever cannot be directly observed (e.g., electrons) must be operationally definable and/or exhibit consistently observable effects. [Note – if an unobservable object/event ψ is “operationally defined,” then the term used to refer to ψ acquires its meaning from the procedures used to quantify or measure ψ.] There is no intuitive, divine, social or textual authority. 

• 3. Verisimilitude (or “Truthlikeness”): 

a. Independent testability – Theories must be independently testable. If a theory is too general to be independently testable, then the component sub-theories of the general theory must be independently testable. For example, evolution is a highly general and not readily testable theory.

However, the primary mechanism of some evolutionary theories is “natural selection.” The process of natural selection can be, and often has been, observed in controlled circumstances. Conversely, the creative power of God, which is a sub-theory of the Creationist view, is non-testable. 

b. Falsifiability – There must be some conceivable way to disprove scientific theories, or, at least, to disprove the component sub-theories of highly general theories. This condition does not mean that such theories are in fact refuted, only that scientists know what it would take to refute them, and hence the refutation of such theories is logically possible. If a scientific theory is actually refuted, then it must be replaced as soon as a more successful alternative becomes available (see next item, and item 4.c below). 

c. Predictive or retrodictive success – All or most of the predictions or retrodictions made by a theory must be accurate within some allowable margin of error. When predictions or retrodictions based on a theory are inaccurate beyond specified tolerances, this is usually considered to be evidence against the theory. [Note – A “retrodiction” occurs when a theory asserts that some event should have happened in the past; the test then involves seeking evidence that this event did in fact occur.] 

d. Boundary Conditions – Must have precise boundary conditions (ideally they would be mathematically precise), such that it is possible to tell clearly and unambiguously whether a prediction, retrodiction or other test has succeeded or failed. 

e. Freedom from Unnecessary Assumptions (or “Ontological Parsimony”) – If a theory (or sub-theory) can explain some given phenomenon without assuming the existence of Φ, then the assumption of Φ is not permitted. For example, if chemistry can explain the phenomenon of combustion without assuming the existence of phlogiston, then assumptions about phlogiston must be excluded. [Note – before Lavoisier discovered oxygen, it was believed that combustion was caused by a substance called “phlogiston” which had properties very different from those of oxygen.] 

Also READ: Is It Possible for God to be Perfect?

• 4. Fruitfulness:

a. Explanatory power – Scientific theories (or component sub-theories) must give independently testable explanations of numerous things or phenomena, usually many more than originally expected. For example, the theory of gravity explained (among other things) the motion of the planets and the behavior of the tides, but this result was not expected when the theory was framed. 

b. Fecundity – Scientific theories lead to the discovery of new phenomena and new problems. These discoveries in turn require new theories and new research programs for their explanation. Hence, scientific theories generate new scientific theories. The new theories are discovered as a direct consequence of the original theory. 

c. Progress – Scientific theories are seldom final. Most theories are expected to fail at some point, and to be replaced by newer, better theories. A theory β is “better” than a theory α if: 1) β exhibits a better fit to the known empirical data than α while satisfying all other necessary conditions (see above and below), and/or; 2) β facilitates the accumulation of greater technological power than α, (see next item). Eventually a subsequent theory γ may exhibit a superior data-fit and/or facilitate greater technological power than β, in which case γ will replace β if and only if γ also satisfies the other conditions (specified above and below) as well as, or better than, β. 

d. Technological power – Scientific theories must enable us to do something that we could never before do; for example, cure diseases, fly, drive automobiles, communicate instantly over long distances, turn on the lights, explore outer space, explore the depths of the ocean, split the atom, create clones, create life in a test tube, build computers, accomplish previously impossible abstract tasks (such as solving Fermat’s Last Theorem), or explain what previously could not be explained within the parameters herein defined. 

• 5. Beauty (or Elegance): 

a. Unification (or Consistency with well-established theory): A scientific theory is not an isolated entity, but part of a complex network which includes all the theories of physics, chemistry, biology, mathematics, astronomy, cosmology, geology, paleontology, archeology, and (arguably) all of the behavioral and social sciences. In order for a theory to be scientific, it must fit consistently with all of these other, well established scientific theories. (A theory which is inconsistent with the larger body of scientific theory would probably also fail the test of logical consistency [see item 1, “Reason”].) 

b. Simplicity (or “Methodological Parsimony”): Given two theories which range over the same logical (or empirical) extension, both of which equally satisfy all other conditions described above, preference must be given to the simpler of the two. 

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