A graded assessment of how comprehensively an explanation accounts for a phenomenon by specifying mechanisms, relevant conditions, range of applicability, and counterfactual dependencies across the scales or levels at which the phenomenon operates.

Principle

Explanatory depth increases when an explanation links observable phenomena to underlying mechanisms and shows how varying key conditions would change the outcome; depth is relative to explanandum, purpose, and the explanatory standards of the discipline.

Demonstration

Illustrative scenario: Two accounts of a disease—(A) reports statistical risk factors; (B) situates those factors in a physiological cascade showing molecular interactions, organ‑level dysfunction, and epidemiological conditions and indicates which manipulations would alter progression. B displays greater explanatory depth because it connects levels and counterfactuals relevant to intervention.

Misapplication

Equating depth with verbosity or number of cited mechanisms rather than with the quality of mechanistic linkage and counterfactual relevance; the mistake is privileging quantity or technical detail over explanatory integration and relevance to the explanandum.

Consequence

Greater explanatory depth typically improves the capacity to generalize, predict consequences of interventions, and identify failure modes; however, pursuing maximal depth can increase complexity, reduce accessibility, and sometimes obscure pragmatic guidance.

Reversal

For some purposes (e.g., real‑time decision making, forecasting) shallower, reduced models with lower explanatory depth may perform better or be more useful; explanatory depth is not always the primary criterion for model selection.

Boundary

Clearly within: mechanistic, multilevel accounts that specify counterfactuals and scope. Boundary case: models offering mechanistic plausibility without full multilevel specification. Clearly outside: purely descriptive summaries or mere labeling without account of mechanisms or counterfactuals.

Semantic Tension

Tension between explanatory depth and simplicity/tractability: deeper explanations can trade interpretability or practical utility for theoretical completeness.

Synthesis

Explanatory depth is not an absolute attribute but a purpose‑sensitive measure: the most valuable explanation links mechanism, scope, and counterfactuals at the level of detail required by the explanatory goal.