hypotheses and theories as synonyms. In general, a theory begins as a hypothesis, and after several tests, if it manages to pass unscathed, it receives the status of scientific theory. However, a 'brand new' hypothesis can be true while a very old theory can be false (do you remember the theory about the Earth being the center of the universe?). This way, with all the logical and scientific rigour, a theory is not necessarily more valid than a hypothesis. New theories can be achieved through induction (which is the most used method), but they can also be achieved through pure imagination, or even dreams [9]. There are no restrictions to create hypothesis. The theories are not refuted by looking at their origins, but at their consequences.5-Pseudo-Sciences There are no restrictions about the origin of scientific hypotheses. A priori, No hypothesis or theory can be discarded only because it was produced from induction or empirical observations. Although this scientific freedom of creating hypotheses can be enriching, since no one is prohibited from creating new and revolutionary scientific theories, it causes, in a terrible contrast, abundance of illogical and absurd theories and hypotheses that reclaim the status of scientific theory: they are the famous "pseudo-sciences."6-Popper and the Falsifiability CriterionThe postulates and scientific methods described herein are adopted, if not explicitly, at least implicitly, by nearly all scientists and philosophers in science. However, they are yet not sufficient to accurately delimit what is scientific and what is not, or to separate science from pseudo-science.We will take, as an illustrative example, the "Green Imp Theory" (GIT): "There is always a 'green devil' hovering over each persons shoulder, but whenever someone tries to look at it, or makes any attempt to detect it or record it somehow, it will get invisible and undetectable. " This example proposes a theory that does not go against any scientific postulate and is not inherently inconsistent, what could be enough reason to reject it, but nevertheless, we are unable to test this theory. So what do we do?The first philosopher who tried to clearly demarcate what is science and what is not was Karl Popper (7/28/1902-9/17/1994) [1]. Popper delimited science by adding the following criteria to it [10]: 1-No scientific theory can be proved true.2-A scientific theory can only be proved false.3-A theory which cannot be refuted is not a scientific theory.Thus, with this new set of postulates, Popper introduced the 'falsifiability' (or refutability) as the main criterion of distinction between scientific and unscientific theories. The refutability of a theory means that, in principle, the theory is liable to be distorted and thus be or not refuted (Modus-Tollens would be a way to refute a theory). For example, when analyzing the case of our Green Imp Theory (GIT) above, we now realize it is not a scientific theory, since it is a theory that cannot be distorted neither directly or indirectly; therefore, it is not refutable and cannot be a scientific theory.It is important to reinforce the idea that there is no "confirmation" of a scientific theory. If a theory passes