Which one of the following is not a feature of Easton's intellectual foundation stones of behaviouralism?

David Easton, one of the most influential political scientists of the behaviouralist school, laid down eight intellectual foundation stones of behaviouralism in his 1965 work, A Framework for Political Analysis, to define its core scientific approach to studying politics. These eight stones together form the methodological backbone of behaviouralism as a movement that sought to make political science more empirical, rigorous, and systematic. Stratification is not one of these eight foundation stones, which is exactly why it stands out as the correct answer among the given options — it simply does not belong to Easton's framework at all.

• Complete List of Eight Stones: Regularities, Verification, Techniques, Quantification, Values, Systematisation, Pure Science, and Integration
• Regularities: Refers to discoverable uniformities in political behaviour, helping form generalisations and predictive theories
• Values: Demands a clear separation between empirical facts and ethical judgements, keeping research strictly value-free
• Pure Science: Recommends postponing the conversion of politics into applied science until pure theoretical understanding is achieved first
• Why Stratification Doesn't Fit: It is a sociological concept tied to social hierarchy and class divisions, entirely unrelated to Easton's scientific methodology for studying political behaviour