The purpose of Directive Principles of State Policy is to

The Directive Principles of State Policy (DPSP), enshrined in Part IV (Articles 36-51), serve as constitutional instructions or recommendations to the State in legislative, executive, and administrative matters [1]. Unlike Fundamental Rights, which are negative obligations prohibiting certain State actions, DPSPs are positive instructions that require the State to perform specific actions to achieve social and economic democracy [3]. They resemble the 'Instrument of Instructions' from the Government of India Act, 1935, providing a roadmap for governance [1]. While they include Gandhian ideals like decentralization (Article 40) and welfare for backward sections (Article 46), these are specific subsets of the broader purpose: to guide State policy at all levels to establish a 'welfare state' [2]. Article 37 explicitly mandates that these principles are 'fundamental in the governance of the country' and it is the duty of the State to apply them in making laws [3].

Sources

1. [1] Indian Polity, M. Laxmikanth(7th ed.) > Chapter 9: Directive Principles of State Policy > FEATURES OF THE DIRECTIVE PRINCIPLES > p. 108
2. [3] Indian Polity, M. Laxmikanth(7th ed.) > Chapter 4: Salient Features of the Constitution > IDirective Principles of State Policy > p. 30
3. [2] Indian Polity, M. Laxmikanth(7th ed.) > Chapter 9: Directive Principles of State Policy > SANCTION BEHIND DIRECTIVE PRINCIPLES > p. 111