Hasok Chang

I develop a concept of observability that pertains to qualities rather than objects: a quality is observable if it can be registered by human sensation (possibly with the aid of instruments) without involving optional interpretations. This concept supports a better description of observations in science and everyday life than the object-based observability concepts presupposing causal information-transfer from the object to the observer. It also allows a rehabilitation of the traditional empiricist distinction between observations and their interpretations, but without a presumption that observations are infallible. Using this concept of observability, I also propose a re-formulation of constructive empiricism that is easier to defend against realist attacks, while open to reasonable realist intuitions.

This chapter advances a contextual view of evidence, through a reconsideration of Hempel's paradox of confirmation. The initial view regarding Hempel's paradox is that a non-black non-raven does confirm ‘All ravens are black’, but only in certain contexts. The chapter begins by reformulating the paradox as a puzzle about how the same entity can have variable evidential values for a given proposition. It then offers a three-stage solution to the reformulated paradox. The situation makes better sense when we reach a deeper propositional understanding of evidence, recognising that each entity can be represented in multiple observational propositions. Some anti-contextualist intuitions can be defused by distinguishing two different senses of the word ‘evidence’, one applying to objects or events and the other applying to propositions; only the latter is relevant to inference. A fuller understanding comes from analysing the constitution and use of evidence in terms of epistemic action. These reflections on the ravens paradox suggest a general philosophical framework more suitable for understanding the function of evidence in scientific and everyday practices.