Does observational knowledge require metaknowledge? A dialogue on Sellars

In the following dialogue between TT - a foundationalist - and WdeV - a Sellarsian, we offer our differing assessments of the principle for observational knowledge proposed in Wilfrid Sellars's 'Empiricism and the Philosophy of Mind'. Sellars writes: 'For a Konstatierung "This is green" to "express observational knowledge", not only must it be a symptom or sign of the presence of a green object in standard conditions, but the perceiver must know that tokens of "This is green" are symptoms of the presence of green objects in conditions which are standard for visual perception.' In the ensuing dialogue, TT argues that it sets the bar too high when knowledge about perceptual conditions is required for ordinary observational knowledge - that young children, for example, are implausibly excluded as knowers given Sellars's principle. WdeV defends Sellars's metaknowledge requirement against these charges. Results from developmental psychology are surveyed for what they show about the actual capabilities of young children. The implications of these results for the success of Sellars's principle are debated.