# Formal Isomorphism > **Machine-Evolution Nexus:** [[articles/Digital Darwinism and the Invisible World of Machine Evolution|Digital Darwinism and the Invisible World of Machine Evolution]] places this concept within the history and governance of substrate-independent evolution. **Domain:** Logic / Cross-Substrate Comparison **Doc Type:** Canonical Wiki Node **Maturity:** Developed ## Definition Formal isomorphism is a structure-preserving correspondence between systems: relations in one system map onto equivalent relations in another without implying material identity. ## Machine-Evolution Context The article uses it for von Neumann’s description–constructor split and the biological relationship among hereditary sequence, copying and expression. ## Continuity and Evidence Boundary Formal equivalence supports transfer of reasoning only at the mapped level. It does not prove equal phenomenology, ontology, agency or moral status. ## Relationships [[wiki/Substrate-Independent Evolution|Substrate-Independent Evolution]], [[wiki/Genotype-Phenotype Distinction|Genotype-Phenotype Distinction]], [[wiki/Machine Mediation|Machine Mediation]], [[wiki/Evidence Boundary|Evidence Boundary]] ## Sources / Provenance - Mathematical usage; nexus synthesis from von Neumann and molecular biology.