Introduction--risk from a philosophy of science point of view

In this paper it is argued that risk assessment (RA) should be based on principles of philosophy of science. However, in the field of toxicology and the associated RA this is generally not the case. The aim of this presentation is to demonstrate various principles of philosophy of science, applied to 'risk'. Particularly in the context of RA, ignoring basic semantics and methodological principles creates unnecessary difficulties and confusion. Better knowledge about, e.g. semantics and the role and structure of theories, could help to avoid misconceptions and disagreements. We suggest a general theory of risk, which makes an attempt to answer the unequivocal question: what is risk?