Towards an Objective Theory of Rationality

6. A Realist Theory of Knowledge

6.1 Theory-Ladenness of Observation Language

Book cover: Perceptual Knowledge by Georges Dicker

That we gain knowledge of an external mind-independent world via our senses is a fundamental axiom of realism. However, this view raises important questions about how our senses function in the acquisition of such knowledge and what methods we use to improve our knowledge. The early empiricist view that by an unbiased use of our sensory organs we may gain direct knowledge about the external world is no longer tenable for a number of reasons. These objections are mostly well covered in the literature, so I shall discuss briefly the two that are most pertinent to developing a theory of rationality. In the process, I will demonstrate the methodological implications for such a theory. The two complications to the empiricist's story of how we gain knowledge of the external world are the theory-ladenness of observation language and the perceptual effects from subjective influences. I will deal with theory-ladenness in this section and leave the discussion about perceptual bias to the following section.

To assert an observation statement about the external world is to assert much more than that the observer is having a particular private sensory-experience. It is to interpret the phenomenological experience in terms of a number of theories. To assert even simple sentences as 'The cat is on the mat' or 'I see a cat on the mat' is to presuppose physical theories concerning the properties of objects called 'cats' and 'mats' and the causal interaction between these physical properties. Whereas in Europe during the middle-ages, people saw some women as witches and some afflicted with a mental illness as victims of demon possession, today we see these same people as quite ordinary women and as people suffering from psychosis. As these examples illustrate, our observation statements are permeated with a host of theoretical presuppositions.

To accept an observation statement as true is also to presuppose some, perhaps relatively inarticulate, theory of observation of how we come to know about the existence of cats, mats, women and the mentally ill and of their properties. If we accept the modern, scientific account of how we visually perceive objects, we will tell the story about how our visual experience of a cat is the result of light waves of particular frequencies and intensities reflecting off the cat, those waves focusing in our retina, electrical signals travelling along our visual cortex to the visual processing areas in our brain and finally resulting in our experiencing a visual image of a cat.

It is in this sense, in which observation terms gain their meaning by being interpreted in terms of a physical theory and in which assertions of observation statements presuppose an observational theory, that we can say that observation terms and statements are 'theory-laden'. The once hoped for theory-neutral observation language on which we could provide a secure foundation for our theories is now seen as a chimera.

The upshot here is that our observation statements are only as precise as the physical and observation theories that they presuppose. In those cases where an observation statement made in support of a new theory presupposes an unsupported observation theory or some other unverified auxiliary hypothesis, prudence demands that we do not accept the observation statement as true. In the following, I will incorporate this lesson into my set of criteria for rational theory appraisal.

Copyright © 2016

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