Skepticism (or methodological or methodical doubt) is a philosophical school of thought within the context of modern empiricism and rationalism, particularly with Descartes. The methodical doubt differs from the skeptical one that is instead: just to doubt and in which doubt is an end in itself for the total lack of confidence in the quality of man. We may say that skepticism use doubt only as a method to test the knowledge in our possession.

The instrument of methodological skepticism does not deny the possibility of true knowledge, as reported by the Greek skepticism. Methodological skepticism can be considered heir of Ockham's Razor and precursor of Karl Popper's falsification. In Descartes, the methodological skepticism proves to be a rationalist tool to judge the value of empirical knowledge. Descartes identifies the end of the doubt in what is evident. Evidence, in fact, is the first point of his epistemological method. Modern thought has taken a rationalist view with Descartes who defined freedom not as a mere "free will of indifference," but as a demanding concrete choice of seeking truth through doubt.

We should remark that Descartes is led by his method to doubt everything, even the world we face; but it has an equally strong conviction that stems from the principle of non-contradiction for which the truth is undeniable, and also that there must be some truth, although it is not known yet where, having to put in doubt the very existence of the world. This creates a cultural tension that seeks to solve this contradiction in the belief that truth is not contradictory and the two propositions can not both be true.

The idea of truth does not exclude doubt, but rather requires it as a necessary tool to look for it and recognize it, without stopping in front of apparent truth. Moreover, the idea of truth does not preclude freedom, indeed it makes it possible, because no choice can be truly free if it is not conscious: man, placed in front of his limits, is constantly faced with the need to choose, then to give up something. We must defend human freedom to choose; but it is a deception the freedom not to choose, that is, to see all claims fulfilled.

The iconoclastic fury of relativism came even to question the existence of objective realities in the field of physical and natural sciences.

Popper said that science - despite having discovered that he could not say definitive certainties - progresses to the truth of nature by increasing approximations.

All the psychic tendencies that are removed from the dogmatic attitude cluster in the unconscious as antithesis and determine the onset of doubts. To defend itself from doubt the conscious attitude becomes fanatic because fanaticism is nothing if not a doubt over-compensated. "

On doubts you can say so many negative sentences: generate laziness, give rise to disbelief, making life anxious and miserable. Descartes is led by his method to doubt everything, even the world we face; but it has an equally strong conviction that stems from the principle of non-contradiction for which the truth is undeniable, and also that there must be some truth, although it is not known yet where, having to put in doubt the very existence of the world. This creates a cultural tension that seeks to solve this contradiction in the belief that truth is not contradictory and the two propositions can not both be true.

 However, there is a positive aspect. It is easy, in fact, to meet people from having certainties so deep to almost reach fundamentalism and to reveal the venom of intransigent despotism. Montaigne, observed that "a vast knowledge brings the opportunity of more doubts."

Who has an extensive knowledge, in fact, notices the complexity of reality and is much more careful to avoid the presumption, the conviction of being possessor of all truth.

The risk is when doubt increases and turns into total and absolute skepticism. The two extremes to be avoided, therefore, are these: do not doubt anything and doubt everything. And this is a rule that can cover all our thinking, acting and living.

To quote Kuhn, fertility of research is in the effort to eliminate contradictions resulting from its forcing reality into rigid and prefabricated categories of its paradigms. The scientific communities that have developed a paradigm just try to solve the problems they can encounter and judge "unscientific", "metaphysical" or even "insignificant" all other problems. At best they consider them too difficult or complex to devote attention. Also, consider ‘sacks’ of disorder to repudiate or minimize any data that do not fit within their paradigm. However, sooner or later, the difficulties and insoluble problems question the paradigm.

This happens in every scientific field, whereby also the paradigmatic structure makes partial and provisional any scientific claim. Consequently, science frames images and descriptions of reality, which do not identify with reality itself. It is known, in this regard, the comparison of Einstein: "Descriptions of the soup is not the soup."

The image of science emerged from historical insights, epistemological, philosophical and sociological of the twentieth century is very different from that of the previous centuries.

The structural limits, imposing and numerous, characterize research, results and knowledge. Abound ambiguities, gaps, misunderstandings, dark areas, disorder, fragile structures, etc., reasons for doubt and uncertainties. Where laymen are dazzled, enchanted, they see irreversible achievements, criticism sees: hypotheses to be proved, unprovable axioms, partial and provisional data, conclusions reformable or unsustainable. There are two very different opposing visions of science. Is it a pure mental construct? Is it limited to appearances or draws from  reality?

For philosophy, science is again in dispute. It studies the many aspects, ideas and reality which intertwine, oppose and overlap each other.

Analytical and critical efforts shall never resolve all disputes. If research must always continue, even reflection on it must remain. Are the problematic characters to make fascinating the study of activity and scientific knowledge; research is on his way towards the results never final.