**6. Epistemology**

It is not superfluous to recall the strong cultural importance of Earth Sciences, which is not obvious: in the past, too many have considered that the science of the Earth, like other scientific disciplines, is simply "technical" and has no cultural depth. Instead, Earth Sciences offer a unique possibility of a conceptualized phenomenon through time and space, in a complex and interactive historical approach.

Understanding how the Earth works requires the retrospection that makes inferences about the past; it requires to interpret the present as the result of large-scale natural experiments: Earth Sciences prepare the ground for understanding the complex relationships between the sciences and for making hypotheses about the possible future.

But the promotion of Earth Sciences as a discipline that most develops ideas of system and complexity, whose understanding is essential to promote scientific skills, requires a strong disciplinary epistemology. Unfortunately, the level of research on epistemology of Earth Sciences is very weak. Earth Sciences, like any scientific discipline, should be based on their epistemology, necessary to face the fundamentals of the discipline, and to define the conditions that allow to build scientific knowledge and to develop methods to reach this knowledge.

But Earth Sciences, unlike other scientific disciplines, have a complex history: from time to time they have faced sociological, economic, technological, and human aspects, from which it has been difficult to break away to develop an abstract epistemological theory. This resulted in a lot of explanations concentrated more on the various components involved, that a search for universal laws, typical of other scientific disciplines [10, 11]. While the philosophy that inspired the work of the founders of modern geology, from Steno to Lyell, between the eighteenth and nineteenth centuries, led directly to a discipline characterized by the principles of identity and unity, in the following years, up to the twentieth century are characterized by research by many of specialists, each attentive to their field, certainly not interested in the epistemological theories of the discipline.

As a global geological theory was far away in time and would still have required many years, everyone was focused on building their own small model, in a reductionist approach, away from the idea of the complexity of the knowledge system. The same happened in the past for Chemistry and Physics. Later, however, chemists and, above all, physicists were able to construct a common language and vision, which led philosophers and historians of science to use these sciences as an epistemological model. In the current model of science, there is a sort of hierarchy that separates the hard sciences from the soft ones, like the natural sciences: Biology and Earth Sciences.

But the specificity of Earth Sciences derives precisely from this fragmentation. It seems particularly useful to develop an epistemology of complexity and in particular it allows to support the idea of non-linearity, useful when the linear model seems too simple and not adequate. In a nonlinear model, every component and every phenomenon must be related to other systems, and it is not possible to find a separate law for each fact. A complex system cannot be static or linear: it is a combination of random processes and non-linear interactions. It is the result of an evolution of the process, in which sometimes it is not possible to recognize relationships of cause or effect between the different components, because both are the result of their common history.

The complexity that characterizes the Earth sciences does not allow to identify a single formal structure of the discipline and is the responsible of its weakness; however, this complexity, due to the presence of so many fields of study that even if in different forms, have to do with the Earth system, is also his wealth [1].
