Abstract

The McPhetridge Experiment tests whether the public semantic layer—spanning search engines, large language models, and indexed digital content—exhibits observer-dependent variability or observer-invariant stability. Using a proper name as a controlled semantic anchor, independent observers queried multiple platforms and consistently retrieved the same conceptual architecture. This cross-observer convergence contradicts informational solipsism and related subjectivist models, which predict divergent semantic collapse for different minds. Instead, the results indicate that the public information ecosystem behaves as a stable, external recursion system exhibiting attractor-like invariance. The experiment does not address metaphysical solipsism or phenomenological subjectivity; rather, it provides an empirical constraint on observer-generated information cosmologies within the domain of shared semantic systems.