For example, if we see one, two, three white swans, we would dare to say: All the white swans are. But at the moment that we saw one black, our theory would be false. Nevertheless, we could affirm: All the white swans are not. It is thus as it advances science. It walks towards the truth although it does not reach it; but whenever a theory is refuted, it will be more near the truth than before. Therefore, to catalogue an argumentation as pseudo-scientist depends on the demarcation criterion that we use.
For example, if we want to know if metaphysics is a science, according to Kant will be it whenever their judgments are synthetic and a priori. We put under if it the criterion of demarcation of the Circle of Vienna, it will not be a science because their conclusions cannot be verified empirically. Popper would not either describe it like science, although it would accept that it owns logic between its judgments and that these are rationally criticizable (although not empirically). But it is not necessary to happen through stop that metaphysics deals with realities that are not sensible, for that reason would be absurd to cause that it demonstrated his validity in a field in which is not applicable. For that reason, at the moment very the criterion of independent demarcation in each science is accepted and that is based on: coherence logical (or internal), verificabilidad of the statements and symbolic precision (to delimit clearly to what each concept or used element talks about). Each science will give different importance from each from these three criteria. Like result, the scientist can know the certainty degree in which the science is placed that is studying. Retaking metaphysics, we verified that it has logical coherence, symbolic precision and a verification that is limited the criticizable thing rationally.