So, just as the concept of Right has to have Wrong as its counterpart to be a truth, so does theory need evidence. Science is a method of understanding, it is an understanding of what exists, what we can determine that we know about these things, and the method by which we go about achieving that understanding. Thus, without evidence on either side of the theory, there can be no support for the theory therefore making that theory non-scientific.
The evaluation of a theory is the identification of the type of theory it is. Much like theories themselves that set out a parameter of evaluation of a measurable prediction about a particular behavior or set of behaviors, theory evaluation is the determination of the validity, structure, and use of the theory itself. Theories have two dimensions: parasitical (its reliance on other theories) and operationalizable (interpretations of the theory). The less parasitical and less operationalizable the theory, the less reliable it is. This means that if a theory does not employ other existing and not disproven theories as its foundation, it has a weaker basis.. So, if I build my theory upon the foundation of other not-proven theories, it will have a stronger foundation....
If there is only one way of looking at a theory, only one interpretation, then it is much weaker for that lack of operationalizability. Thus, if I have a theory that people diagnosed with Attention Deficit Disorder (a disorder that has been theorized, evidence has been found, and has been since classified and codified) are more likely to get into car accidents than people without ADD, I have all existing cognitive theory regarding mental function and ADD, all theory of physics and hand-eye coordination as well on my side. In terms of interpretation, we can see this from a variety of angles.
The field of psychology requires a very stringent theoretical approach. Because mental health is a field that has less measurable objects than other sciences, it requires a more stringent approach to its theoretical design. Scientific Psychology requires an understanding of Monism in the mind/body study, of non-conscious behavioral control, the belief that people are variable yet predictable, and that evolution is central to the development of humanity. These aspects are what mark psychology as a science rather than a folk concept.
