Observer-Dependence

Observer-dependence is the principle that the properties, structure, and even existence of phenomena depend on the observer's frame of reference, instruments, or cognitive apparatus. In quantum mechanics, it is literal: measurement determines the state. In social systems, it is structural: a community exists as a community only for observers who share the distinction 'member/non-member.' In cognition, it is foundational: what counts as an object, a cause, or a pattern depends on the observer's categories and goals.

Observer-dependence is not relativism. It does not claim that all observations are equally valid. It claims that validity itself is observer-dependent: the criteria of truth, evidence, and coherence are generated within specific observing systems and do not transcend them. A scientific observation is valid by scientific criteria; a legal observation is valid by legal criteria. The criteria are not arbitrary, but they are not universal either. They are the products of historically specific systems of observation.

The concept is closely related to observational closure: the observer cannot observe the conditions of their own observation, and therefore cannot access a 'view from nowhere' that would validate or invalidate all other views. But observer-dependence adds a further claim: different observers, with different closures, genuinely see different worlds. The worlds are not illusions; they are the real products of real observational operations. The task is not to reduce them to a single world but to understand how they are coupled, how they interfere with each other, and how their mutual observation produces the appearance of a shared reality.