The Regional Ontologies
In ordinary discourse, as well as in scientific discourses, we use a great variety of declarative sentences that we qualify as true (for instance, “2 + 2 = 4”, “Paris is the capital of France”, “insects have six legs”, “gold is more expensive than silver”, “Hector is a Trojan warrior in the Iliad”, “Napoleon was defeated at Waterloo”, “Spanish is a neo-Latin language”, “the Earth is a planet in the Solar system”, the “Minotaur lived in Crete”).
Since, as we have stressed above, a true sentence cannot be true “about nothing”, the “fact” to which it refers must obtain, must be the case. It follows that also the entities mentioned in the declarative true sentence, as well as the properties and relations of these entities, must exist, though having kinds of existence very different in the different cases. So we can say that 2 is a mathematical entity, or has a mathematical existence; that Paris and France are geographical (or political) entities linked by the geographical (or political) relation of the first being the capital of the second; that Hector is a literary person or has a literary existence; that the Minotaur is a mythological entity or has a mythological existence. This way of speaking sounds very obvious, but it actually has a deep significance: it recovers the fundamental thesis of Parmenides that being simply is what is different from non-being, that is, from nothing, and at the same time retains the equally fundamental Aristotelian thesis of the analogical sense of being. Aristotle has presented this thesis especially regarding the “way of being” or existing (for example, the substance exists “in itself’, whereas the accidents exist only “in a substance”; or something can exist “in potentiality” or “in actuality”). Our examples have to do with another aspect of the analogy of being, that is, with the different “kinds of existence”, that were also considered in the philosophical traditions and have been revisited in the Husserlian doctrine of the regional ontologies. The temptation that must be resisted (at least in the present discourse) is that of trying to distinguish what “really exists” from what exists “only in a certain sense”, a distinction that sometimes is presented as a difference between metaphysics (the discourse regarding what really exists) and ontology (the discourse regarding only thinkable or even fictitious entities). Very easily one may think that ‘what really exists' is what exists in space and time, but how could we deny real existence to a deep sorrow that might push a person even to suicide, or to a bankruptcy that could suddenly reduce to poverty hundreds of people? Not to speak of the numberless people who believe in the existence of an immaterial god or a plurality of immaterial deities. The risk of such a pretension is to fall into a flat reductionism by dogmatically stating that a certain kind of reality is what “really exists” and then trying to reduce all the rest to a manifestation of that reality (which would be an unconscious form of uncritical metaphysics).We can avoid such difficulties because we have explained how all these different “entities” about which a certain declarative sentence is true are its referents and, in addition, we have also explained how certain fundamental referents of a scientific discourse can be immediately attained by specific operations that play the role of criteria of referentiality and criteria of truth for the specific discipline adopting them.
Therefore, if I say that I saw a white horse in a dream, whereas I actually saw a black cat, my declaration is false and it would not be correct to say that it is neither true nor false, because these horse and cat “did not exist”. Indeed they exist in the ontological region of the dreamed entities, that may have a not negligible place in a person's life, be the subject matter of literary works, and even become an important source of “data” for certain scientific theories such as psychoanalysis. Let us note, in addition, that the domain of referents, or ontological region, delimited by a certain group of concrete material operations is not necessarily material: for example, in order to ascertain whether it is true that Hector was a Trojan warrior in the Iliad, one needs to perform concrete operations like finding a book in a library, visually recognizing that its title is Iliad, reading it in a language that he knows, and finally finding out whether there is in that book the story of a certain personage named Hector playing the role of a Trojan warrior.
This literary personage is not material and has just a literary existence.This simple example helps us in clarifying that the operations used in an empirical science for determining its domain of reference are certainly material, and are the tools for recognizing immediately true or false statements. They provide the data of the science in question and for this reason are also the tools for testing the acceptability of other statements that are not fully expressed by means of operational predicates (by checking whether such statements logically entail operationally testable consequences). The construction of the most important sciences, however, goes far beyond the collection of such immediately true statements and, as we have seen, introduces new concepts by means of definitions and proposes theories in order to explain data. This amounts to introducing certain abstract objects that encode concepts not all of which are of an operational nature and which, therefore, cannot be exemplified by means of the concrete basic operations.
What is the ontological status of such objects? We can answer that their ontological region remains that determined by the fundamental operations: they are physical objects if they are introduced in a physical theory and do not convert themselves into literary, psychological or mathematical objects. Yet this answer is not totally clear. One can say: of course, as abstract objects they certainly exist and belong, for instance, to physics, but do they really exist? That is, are they also exemplified by physical referents? This is the core of the issue of scientific realism that, in its rough formulation, can be expressed as the question of the existence of the unobservables and remains intact also after having refined it by replacing the observations by the operations, as we have done.
9