Against the ideological use of this notion, one must specify that if correctly understood, “relativism” is a tertium genus between rationalism and scepticism, between fundamentalism nihilism. This middle way between an excessively conceited reason and one that is excessively defeatist, involving both the fields of science and of ethics. In science relativism means the rational impossibility to prove the truth of theories with certainty. It was above all Alfred Tarski, with his Semantic theory of the truth, who proved that it is logically impossible to prove the truth of any empiric theory, since to prove that a theory is certainly true one should prove as true all its consequences, a logically impossible operation since these would be of an infinite number.

Scientific truth should therefore not be understood as a certainty, but as a controllable possibility based on the principle of falsifiability, hence on the continuous revision of existing theories, correcting any eventual mistakes. This relativism of the Popper kind should not be confused with the sceptical relativism of those – such as Th. Kuhn, P. Feyerabend and the “new sociologists of science” who like D. Bloor propose a so-called “strong programme” – proposing a sort of epistemological egalitarianism, which renounces not only the notion of certainty but also those of truth and objectivity. Hence there is no scientific truth, but many ethno-truths, all epistemologically legitimate, since many are the forms of life. Since the “truths” are incommensurable because determined by different cultural frameworks, the scientist would not be capable of exercising precisely that critical faculty that historically has allowed the growth of scientific knowledge. Rather then relativism, in this case it would be more correct to speak of a form of scepticism (the natural consequence of collectivistic sociologic events) rejecting the idea of progress made by scientific knowledge.

In the field of ethics too the traditional philosophy of critical rationalism (among others that of Mill, Popper, Albert and Bartley), helps us define a position that is neither foundationalistic, nor irrationalistic. It was David Hume who proved that, since from descriptive propositions that speak of facts one can logically deduct only other descriptive propositions and never normative propositions, then values cannot logically derive from facts. Only one ethical proposition can derive from the propositions of science: ethics assess and science explains. Ethical decisions do not derive from facts, but are based on the individual conscience: it is the conscience that judges facts. The “law of Hume” establishes freedom of conscience, because it proves impossible rationally based ethics (on the basis of theological, biological, anthropological, economic principles etc), valid erga omnes, that someone might be the bearer or discoverer of and perhaps feel legitimated to impose on others.

“Ethical relativism” is therefore at the basis of an ”open society”, which is a public order in which there is room for the highest possible number of conscience choices that are compatible among themselves, and that respect the rules of the state of law. It is not therefore a coincidence that the great defenders of democracy (from Mill to Popper, from Kelsen to Hayek) saw precisely in the unreasonable expectations of reason the main threat to individual freedom. All totalitarian regimes in fact are the result of a persuasion, nourished by an ideology, a philosophy, a theology or a scientific theory, or one presumed to be such – knowing in a definitive manner what is Good and what is Evil; and those with such a persuasion feel naturally invested with the historical mission of imposing it upon those who have no awareness, whatever the cost may be.

While on one hand this ethical relativism proves the non sustainability of the fondamenta inconcussa, on the other it does not state that those ethics are irrational choices, the effects of causes (social, economic, biological, etc) that differ from individual reasons and that annul subjective intentionality. If science is without certainty but not without truth, ethics are without truth but not without reasons: behind every decision there are the reasons of individuals who intend to solve problems, interpreting determined situations. Critical discussion, the comparison between ethical proposals is possible, on one hand because there is no scientific criteria for establishing what is right and what is wrong, and on the other hand because homo etichus is not a puppet without intentionality and reason, manoeuvred by set-ups of various kinds.

Dialogue, also in the field of ethics, requires two conditions: that there should be no one thinking they have an absolute knowledge and that there should be a rationally communicable content. And if within science a dialogue is needed to identify and remove errors that are inter-subjectively acknowledgeable, in the field of ethics it is needed to emphasise the presuppositions and consequences of moral decisions, so that these choices, which however remain the choice of consciences, are adopted with “open eyes”, on the basis of a correct point of balance between the “ethics of intention” and the “ethics of responsibility”. Finally, this “ethical relativism” understood as such reveals itself as a powerful means for the criticism of “cultural relativism”, understood as often happens as meaning that cultures are separate forms of life, communicating universes that preclude therefore all inter-cultural debate. If ethical options cannot be empirically founded, then they also cannot be perceived as the mere effects of a given context (cultural, social, and economic).

If the “law of Hume” is valid, there cannot be as many morals (and in addition incommensurable ones) as there are forms of life, but there will be as many ethical decisions, all equally not absolute and each differing from the other, as there are individuals. Individuals are certainly immersed in cultural traditions, which, however, should be understood as a heritage of ideas that some individuals pass on to other individuals and that condition but do not determine their moral choices. Hence there cannot be a privileged moral, neither as far as the emancipation of a certain environment is concerned, nor as the emanation of a given environment (ethno-centrism), nor because established by an individual (a philosopher, a dictator) who thinks he has absolute knowledge.