1. The existence of a fundamental symbolic model called General Communication Language (GCL) is supposed. This symbolic model contains absolutely all words, together with their definitions. The definitions can be more or less precise, logically consistent or not, can be or not accepted by some or others. GCL is the common language formed spontaneously between people in their inter-relations along the milleniums. 2. We choose a word (term) T from GCL. 3. Let's suppose that there is a positive science SM, that could include the term T. 4. The term T, that should be studied by SM, has to be included in SM. For this purpose, T has to be redefined within the frame of SM. SM can integrate a new term only if this term is defined within SM. Thus T will have one definition in GCL and another generated by SM.
Example: The term 'force' has one definition in GCL and another in Newton's Mechanics. The predictions of Newton's Mechanics refer only to the term 'force' as it had been defined within Newton's Mechanics.
5. As soon as T has been included in SM, SM generates the relationships between T and other elements, and makes predictions that include T. These predictions can then be compared with external reality. 6. If the predictions of SM related to T prove to be acceptable, then SM is considered useful in understanding T. If the predictions are unacceptable, then SM is inadequate in understanding T. In neither case, SM can be considered correct or incorrect. 7. Any prediction connected to T has to be associated with the SM which produced it.
Example: Gravity is a supposition of Newton's theory. In his theory gravity is a property of the mass of a physical body. In Einstein's theory (another symbolic model), gravity is a property of space and mass. Both theories give good predictions in known specific situations.
8. As the predictions of SM related to T are proved acceptable, SM is considered suitable in understanding T and thus, the predictions of SM including T can be associated with the term knowledge.
Knowledge based on an acceptable SM is the purpose of any positive science.
We'll see now an extremely complex example. We have intentionally chosen a term which practically has no definition in GCL (the definitions is unclear) and has no associated direct data and facts from the external reality. The term chosen is 'alien' (ET).