The so-called ontological naturalism is the thesis that ontological work-that is, the investigation of what exists-constitutes a purely scientific task. Philosophy (metaphysics, in particular) has little or nothing to contribute to this research. The authors argue that this is not viable. 1. SIX FUNDAMENTAL METAPHYSICAL PRINCIPLES Language is related to the origin of the systemic conception of Reality. Language may be defined as a symbolic substitute of Reality, or as a system of signs. Following a more or less classical approach to Reality, different classes of objects exist, that are characterized by different mental acts through which we distinguish them from their surroundings (Meinong, 1904). Objects of sensorial perception, in this approach, are different from objects of thought, but these latter ones are not less "objective" than the previous ones: the former are apprehended through thought but it does not constitute them. According to the terminology of Meinong, meaning subsists, whereas individual beings and qualities exist. In this sense, objects of thought can be real without existing in the technical sense defined by Meinong. Mathematical objects are of this class. The first condition is that these objects are there, and this does not happen through an act of discourse, but through the presence of these objects in the Subject's thought (Agazzi, 1992). The phenomenological situation is perhaps that an object, simply by the fact of being present, offers to the Subject an irrefutable and particular witness of itself. The referential situation is the phenomenological presence of the object. And the truth of a sentence is the coincidence between the situation and its phenomenological presence. It is to notice that meanings or understandings are only partially faithful with respect to any particular phenomenological presence or referential situation that they could denote. Some form of modalization (alethical, Deontical or doxical) necessarily accompanies the communication. There is a clear epistemological separation between thought and language. All organization of a language depends on a complex structure. Biunivocal correspondence between the perception of Reality and the linguistic system is unthinkable. One operates from a superior order, from a mesosystem that would include them and in which both appear as elements and not as closed and independent units. Horizontal forces of all systems are those that determine their potential of significance. This means that no language is neutral, and that any representational space is not neutral either. That is to say, the systemic conception, as any other semiotic conception, represents Reality in the same way as other systemic conceptions. By virtue of what we have just written we can propose the following principle: