**Extended Abstract**

Modern constitutionalism has traditionally been concerned with the limitation and control of political power through legal and institutional mechanisms. Yet, the contemporary transformation of the state and the increasing complexity of political, social, and legal relations have made it increasingly difficult to understand constitutionalism solely in terms of institutional arrangements for constraining power. Constitutional institutions must not only be capable of controlling power effectively, but must also derive their authority from normative values that can justify their exercise and sustain their legitimacy. This situation raises a fundamental question concerning the relationship between two forms of rationality that have played a central role in modern political and institutional thought: instrumental rationality and value rationality. The central problem of this research is therefore not to choose between institutional efficiency and normative legitimacy, but to explain how these two dimensions can be connected within the process of constitutional institution-building.

The main research question is: **What relationship should exist between instrumental and value rationality in constitutional institution-building so that a constitutional system can avoid both the domination of purely functional institutionalism and the instability resulting from idealism without effective institutional foundations?** The research hypothesis is that the appropriate relationship between the two forms of rationality cannot be established through the separation or predominance of one over the other. Rather, it requires a dynamic, dialectical, and feedback-based relationship in which institutional effectiveness provides the necessary conditions for the concrete realization of constitutional values, while normative legitimacy provides direction, justification, and long-term sustainability for institutional effectiveness. Accordingly, efficiency and legitimacy should be understood not as mutually exclusive alternatives, but as mutually conditioning dimensions of constitutional rationality.

The research adopts a **descriptive-analytical method with a comparative-historical approach**. The materials of the study have been collected through documentary and library-based research, drawing upon theoretical, philosophical, legal, and historical sources concerning rationality, constitutionalism, institutionalism, and constitutional development. The theoretical framework is constructed through a critical reconsideration of **Max Weber’s distinction between instrumental and value rationality**, **Jürgen Habermas’s theory of communicative rationality and practical discourse**, and the major approaches of institutionalism, including **historical, rational-choice, sociological, and discursive institutionalism**. Weber provides the conceptual foundation for distinguishing the two dimensions of rationality, while Habermas offers a theoretical basis for overcoming the limitations of a purely instrumental conception of rationality by connecting legitimacy with communicative processes and practical discourse. Institutionalism, in turn, makes it possible to translate these theoretical insights into an analysis of institutional structures, historical trajectories, actors, norms, and processes of institutional reproduction.

The study argues that instrumental rationality has an indispensable role in constitutional systems. Constitutionalism requires effective institutional arrangements capable of limiting arbitrary power, distributing authority, monitoring public officials, and providing procedures for accountability. Separation of powers, independent judicial review, oversight mechanisms, administrative control, and institutional feedback mechanisms are among the manifestations of this dimension of rationality. Nevertheless, when institutional efficiency becomes detached from normative commitments, constitutional institutions may be reduced to technical mechanisms of administration and control. In such circumstances, institutional rationality may generate bureaucratic domination, weaken public trust, and ultimately produce a form of effectiveness that lacks sufficient normative legitimacy.

Value rationality responds to a different but equally fundamental dimension of constitutionalism. Constitutional institutions are not established merely to make the exercise of power more efficient; they are also intended to protect and realize values such as freedom, equality, justice, human dignity, and collective self-government. Nevertheless, value commitments cannot by themselves guarantee the effective realization of these principles. When normative ideals remain disconnected from institutional procedures and organizational capacities, they may become politically ineffective and incapable of producing stable constitutional arrangements. The central argument of the study is therefore that neither instrumental rationality nor value rationality is sufficient in isolation.

On this basis, the research proposes a **Model of Functional Dialectical Equilibrium** as an analytical framework for understanding the relationship between efficiency and legitimacy in constitutional institution-building. The model conceptualizes constitutional rationality as a continuous process of interaction and mutual feedback rather than as a fixed division between technical and normative spheres. Within this framework, three institutional indicators are identified as particularly significant: **the institutionalization of independent interpretive procedures, the formation of overlapping discourse concerning fundamental constitutional values, and the internalization of professional ethics among institutional actors**. Independent interpretive procedures prevent institutional mechanisms from becoming entirely subordinated to political power; overlapping normative discourse connects institutional arrangements with shared constitutional values; and internalized professional ethics enables institutional actors to comply with constitutional norms not merely because of external sanctions, but because of an internal commitment to legal and constitutional principles.

To examine the explanatory capacity of the proposed model, the study comparatively considers the historical experiences of **England, the United States, and France**. The purpose of this comparison is not to reconstruct their constitutional histories in their entirety or to establish historical equivalence among them. Rather, these cases are examined in terms of the interaction among the three identified institutional indicators and the ways in which their presence or absence affected the relationship between efficiency and legitimacy. The comparative analysis demonstrates that constitutional stability cannot be adequately explained either by institutional engineering alone or by the existence of normative ideals independently of institutional structures.

The findings ultimately indicate that the relationship between instrumental and value rationality should be understood as a **dynamic dialectical relationship**. Instrumental rationality is necessary for transforming constitutional values into effective institutional arrangements, while value rationality is necessary for determining the purposes, limits, and legitimacy of institutional power. The absence of either dimension creates a structural imbalance: the dominance of instrumental rationality risks producing bureaucratic and technically efficient institutions without adequate normative legitimacy, whereas the dominance of value rationality risks producing constitutional aspirations without sufficient institutional capacity for implementation. The proposed model therefore reframes constitutional rationality as a process of continuous adjustment, interpretation, and feedback between institutional performance and normative justification. The study concludes that the sustainability of constitutionalism depends not upon the elimination of the tension between efficiency and legitimacy, but upon the institutionalization of mechanisms capable of transforming this tension into a productive and continuous process of constitutional development.