Theory is derived from the earlier proven formulae. In sanskrit language, there are two aspects - 'samanya' and 'visesha'. Samanya is what we see once and again. For example, this crow is black, that crow is black, the other crow is black. So theory is derived as 'every crow is black'. Of-co0urse there are exceptions and some one may claim that he has seen a white crow. But, the wise knows that it means not the crow of which we proved about.
Same way, One theory that was not proved to its extremity or entirety, but 91.6% true and proved, could be applicable in psychology on the risk that more than certain percentage it would be useful.
Thus the most experienced Medical Officer advises "to take this tablet or capsule for 5 course and let me know the result" to escape from the promise of 100% recovery of the patient.
Many ideologies stem from older theories. The ideas of the philosophers are simplified. Ideologies
Early in the twentieth century, when malnutrition was common, companies such as this one advertised
Major Events in the History of Psychology (2 of 6)
Major Events in the History of Psychology (6 of 6)
Stages Theories of Grief
Psychology and Life