Formal Sciences
Logic
Model Theory
ElementScope CategorySub-ItemDefinitionStructures, Languages & Interpretations
1. Domain1.1 Scope of the DomainBoundariesThe range of phenomena the science includes and excludes.Concerned with formal languages, structures, signatures, and interpretations; includes domains, functions, relations, and symbol assignments. Excludes semantic content not expressible in first-order definability.
ScaleThe spatial, temporal, or organizational level at which the science operates (e.g., quantum, cellular, social, cosmic).Operates entirely at the formal/logical scale: symbolic expressions, abstract structures (sets with relations/functions), and homomorphic mappings between them.
1.2 Ontological CommitmentsEntitiesThe kinds of things assumed to exist within the domain (particles, organisms, agents, fields, etc.).Structures (𝔐), domains (
PropertiesThe fundamental attributes these entities possess (mass, charge, genotype, preference, etc.).Arity, interpretation of symbols, definability, satisfaction, isomorphism type, elementary equivalence, and preservation properties under embeddings.
CategoriesThe basic ontological types used to classify domain elements (substances, processes, relations, structures).Languages, signatures, term algebras, formulas, structures, morphisms (homomorphisms/embeddings), definable sets/functions, elementary diagrams, substructures.
1.3 State-VariablesVariablesThe measurable or definable properties that describe system conditions.Assignments, valuations, tuples from the domain, truth values of formulas under interpretations, definable element-sets, definable functions.
ParameterizationHow variables encode and represent the system’s state.Parameterization through substitution of variables with domain elements, interpretation of nonlogical symbols, and the satisfaction relation 𝔐 ⊹ φ(ā).
1.4 Admissible IdealizationsSimplificationsConceptual reductions used to make the domain tractable (point masses, rational agents, perfect gases).Treat languages as fixed and finite; treat structures as set-theoretic; assume closure under substitution; ignore computational or cardinality constraints; assume exact symbolic interpretation.
Validity ConditionsThe limits and contexts in which idealizations hold or break down.Break down with higher-order semantics, infinitary languages, ultraproduct anomalies, category-theoretic semantics, or failures of definability or compactness assumptions.
1.5 Domain AssumptionsStructural AssumptionsBackground ontological stances such as determinism, continuity, randomness, discreteness.Assumes classical first-order logic, Tarskian semantics, bivalent truth conditions, standard set-theoretic foundations, and stable interpretation of language symbols.
Implicit CommitmentsUnstated but necessary assumptions that shape the field’s conceptual structure.Assumes satisfaction is absolute under isomorphism, definability behaves predictably, diagrams encode structures faithfully, and embeddings preserve the essential logical structure.
1.6 Internal Coherence RequirementsConsistencyThe demand that domain concepts do not contradict one another.Requires consistent signatures, coherent interpretation of symbols, and non-contradictory satisfaction assignments across structures.
CompatibilityThe requirement that entities, variables, and assumptions fit together into a unified descriptive framework.Requires formulas, structures, embeddings, and interpretations to align; satisfaction invariant under isomorphism; substructure and diagram relations consistent with signature constraints.
2. Evidence Layer2.1 Observable PhenomenaObservablesThe aspects of the domain that can produce detectable signals accessible to measurement.Truth values of formulas in structures, definable sets/functions, satisfaction patterns, homomorphism behavior, embedding properties, isomorphism invariants.
Detection LimitsThe boundaries of what can be resolved or sensed by current instruments or methods.Limits set by expressiveness of the language: first-order inability to distinguish elementarily equivalent models, undefinability of certain sets, compactness constraints, Löwenheim–Skolem bounds.
2.2 Measurement SystemsUnitsStandardized quantifications (meters, seconds, volts, decibels, dollars, etc.) necessary for consistent comparison.Logical units: arity, quantifier rank, formula complexity, cardinality of language, size of domains, degree of definability.
InstrumentsDevices and tools (microscopes, spectrometers, sensors, surveys, detectors) used to produce measurements.Logical tools: satisfaction relation (⊹), diagrams, syntactic calculi, homomorphism tests, embedding tests, back-and-forth systems, Ehrenfeucht–FraĂŻssĂ© games, type spaces.
2.3 Operational DefinitionsDefinitionsTerms defined by specific measurement procedures, ensuring empirical clarity.Definability via formulas; interpretation of terms, relations, and functions; elementarily definable sets; schema-based definitions; diagrammatic encodings.
ProceduresThe explicit steps required to perform a measurement in a reproducible way.Evaluating satisfaction 𝔐 ⊹ φ(ā); constructing diagrams; checking embeddings; performing EF-game rounds; computing types; verifying preservation under maps.
2.4 Data AcquisitionProtocolsFormal processes for gathering data under controlled or standardized conditions.Constructing structures, substructures, and elementary extensions; forming reducts/expansions; evaluating definability; applying Tarski–Vaught criteria.
SamplingRules determining which subset of the domain is measured and how representative it is.Choosing representative tuples, definable subsets, types, or finite partial isomorphisms; selecting fragments of structures (finite subdiagrams).
2.5 Data Character & FormatData TypesThe form raw evidence takes (time series, spectra, images, counts, qualitative records).Formulas, types, satisfaction data, diagrams, elementary embeddings, EF-game outcomes, definable sets/functions, isomorphism invariants.
ResolutionThe granularity or precision with which data is captured.Fineness of logical discrimination: quantifier rank, alternation depth, expressive power of language, complexity of formulas, precision of type classification.
2.6 Reliability & CalibrationCalibrationAdjustment procedures ensuring instruments produce accurate results.Ensuring mappings preserve structures: verifying homomorphisms, embeddings, and elementary embeddings; calibrating definability by equivalence of formulas.
Error CharacterizationIdentification and quantification of noise, uncertainty, bias, and measurement error.Logical error sources: misinterpreted signatures, incorrect substitution, failure of preservation, non-elementary embeddings, ambiguity in definability, compactness/pathology effects.
3. Structural Layer3.1 Patterns & RegularitiesLaws / RelationsStable, repeatable patterns governing how observables behave across conditions.Satisfaction relation 𝔐 ⊹ φ(ā); preservation theorems; compactness; completeness; Löwenheim–Skolem effects; definability patterns.
InvariantsQuantities or properties that remain constant under transformations (symmetries, conservation laws).Isomorphism type, automorphism groups, definable closure, elementary equivalence, quantifier-rank invariants, back-and-forth invariants, type spectra.
3.2 Causal ArchitectureMechanismsUnderlying processes or structures that produce the observed regularities.Logical consequence, definability mechanisms, preservation under embeddings, ultraproduct construction, type realization, diagram expansion.
PathwaysOrganized sequences of interactions forming a causal chain or network.Chains of embeddings, elementary chains, back-and-forth sequences, saturation pathways, construction of models via diagrams or Fraïssé limits.
3.3 Theoretical VocabularyConceptsCore terms that encode the domain’s structure (force, gene, equilibrium, field).Structure, signature, language, formula, term, model, theory, type, elementary substructure, quantifier rank, definability, interpretation.
ClassificationsTaxonomies, categories, or typologies that organize entities and relations.Model classes, theory classes (stable, unstable, simple, o-minimal), isomorphism classes, definable sets, saturation levels, algebraic vs. elementary closure.
3.4 Formal RepresentationsEquationsMathematical constructs expressing laws, relations, or mechanisms.Logical equivalences, satisfaction relations, definitions of embeddings/isomorphisms, compactness statements, ultraproduct constructions.
ModelsStructured representations—mathematical, computational, or conceptual—used to predict and explain phenomena.Structures interpreting a language; elementary extensions; reducts/expansions; saturated models; prime models; limit models; ultraproduct models.
3.5 Idealized StructuresSimplified ModelsPurposeful abstractions that capture essential dynamics while omitting irrelevant detail.Pure relational structures; pure sets with simple signatures; finite substructures; atomic diagrams; toy models for definability.
Limit ConditionsRegimes where specific models or approximations hold (classical vs. quantum, linear vs. nonlinear).First-order expressiveness boundaries; compactness-induced phenomena; non-definability regions; breakdown under higher-order or infinitary languages.
3.6 Integrative FrameworksUnifying TheoriesHigher-order structures that connect disparate laws or mechanisms under a coherent whole.First-order logic, Tarskian semantics, model-theoretic stability theory, classification theory, interpretability theory.
Interdisciplinary LinksPoints where the theory connects to adjacent sciences or larger explanatory systems.Links to algebra (groups, fields, modules), topology (Stone spaces), combinatorics (Fraïssé limits), computer science (automata, formal languages), and category theory.
4. Method Layer4.1 Inquiry DesignExperimental DesignStructured plans for manipulating variables to test causal claims.Varying languages, signatures, or axioms to test definability, preservation, elementary equivalence, or expressiveness. Constructing alternative structures to probe logical distinctions.
Observational DesignSystematic approaches for gathering non-manipulated data (surveys, field studies, natural experiments).Studying models without manipulating them: examining satisfaction patterns, definable sets, type spaces, EF-games, or automorphism behavior.
4.2 Testing & ValidationHypothesis TestingProcedures for evaluating whether evidence supports or contradicts specific claims.Checking whether structures satisfy specific sentences, whether embeddings preserve formulas, whether two models are elementarily equivalent, or whether definability claims hold.
ReplicationThe requirement that results be independently reproducible under similar conditions.Reproducing satisfaction results across isomorphic structures; repeating definability tests across extensions, reducts, or ultraproducts; verifying EF-game outcomes.
4.3 Inference & EvaluationStatistical InferenceRules for drawing conclusions from noisy or incomplete data.Logical analogs: extracting invariants from EF-games, analyzing type frequencies, counting realizations of formulas, studying definability spectra.
Model ComparisonCriteria (fit, simplicity, predictive accuracy, robustness) used to evaluate competing models.Comparing structures or theories by expressive power, quantifier complexity, definability strength, type behavior, saturation, or classification-theoretic profile (stable vs. unstable, simple vs. complex).
4.4 Error ManagementError AnalysisIdentification and quantification of random and systematic errors.Identifying failures of embeddings, misinterpreted signatures, incorrect substitutions, definability errors, compactness misapplications, or non-elementary embeddings.
Bias ControlMethods for minimizing subjective, instrumental, or procedural biases.Ensuring neutrality in language choice, avoiding overfitting via overly rich signatures, preventing selection bias in chosen substructures or types, controlling assumptions in diagrams.
4.5 Adjudication & RevisionPeer ScrutinyCollective evaluation of claims through critique, review, and debate.Critical examination of definability claims; reviewing preservation theorems; evaluating construction methods (ultraproducts, diagrams); refining classification results.
Theory RevisionProcedures for modifying, replacing, or discarding models based on new evidence.Adjusting axioms, languages, or interpretations; revising diagrams; modifying theories to reflect newly discovered preservation failures or definability boundaries.
4.6 Integrity ConditionsTransparencyRequirements to disclose methods, data, assumptions, and limitations.Full specification of signatures, languages, structures, diagrams, embeddings, EF-game parameters, and construction methods.
Ethical StandardsNorms ensuring responsible conduct in experimentation, data handling, and publication.Intellectual honesty in definability claims; accurate reporting of preservation limits; clarity in assumptions; proper attribution of theorems and constructions.