Abstract
Recently we have learned how experiment can have a life of its own. However, experiment remains epistemologically disadvantaged. Scientific knowledge must have a theoretical/propositional form. To begin to redress this situation, I discuss three ways in which instruments carry meaning: 1. Scientific instruments can carry tremendous loads of meaning through association, analogy and metaphor. 2. Instrumental models of complicated phenomena work representationally in much the same way as theories. 3. Instruments which create new phenomena establish a new field of material possibilities. I suggest that scientists employ a "visual/physical/material logic," analogous to propositional logic, which establishes relations between different material forms.