Javier Silva Silva

The goal of this thesis is to propose a naturalistic definition of mental disorders. Naturalistic theories about disease generally attempt to establish what makes a biological phenomenon a disease by relying on the concept of biological function, stating that diseases and biological dysfunctions are equivalent. This implies the need to ground normative judgments on supposedly objective phenomena, which conflicts with descriptive scientific discourse and opens the gate to rebuttals on the supposed objective nature of diseases. However, at least theoretically, the failure of the dysfunction definition of disease does not necessarily imply the failure of the naturalistic programme. The claim that the usual definition of disease as biological dysfunction is not the only possible way of defining disease in a naturalistic fashion will be defended. To back the previous claim, a definition of disease that does not depend on normative nor subjective criteria will be elaborated. It is argued that the 'negative' aspect of diseases should be understood in terms of a decrease in rate of change of the probability of living until a certain moment in time, and that diseases are processes related to negative impact on the viability of a biological organism. As will be shown, this proposal has potential as a solid naturalist alternative, with which disease naturalism can withstand arguments against the supposed subjective nature of dysfunction-based theories by resorting to this new proposal. Following this line of argumentation, empirical evidence about paradigmatic cases of mental disorders, such as schizophrenia, bipolarity and melancholy, can be invoked to argue that mental disorders can satisfy the criteria of being a disease by virtue of generating an increase in the probability of experiencing a negative impact on viability. Hence, this proposal shows promise in explaining the reason why mental disorders should be considered pathological.