Who said that the ‘Directive Principles are merely furthering the goal of social revolution’?

Directive Principles are not enforceable by the courts. The sanction behind them is political. As Dr. Ambedkar observed in the Constituent Assembly, 'If any government ignores them, they will certainly have to answer for them before the electorate at the election time'. The DPSP is a part of the Constitution. Article 37 unequivocally enjoins that 'it shall be the duty of the state to apply these principles in making laws'. Hence it should be competent for the Union to issue directions against particular states to introduce compulsory education for children (Article 45), to prevent slaughter of cows (Article 48) and to bring about prohibition of alcoholic drinks (Article 47). In case of refusal to comply with such directions issued by the Union, it may apply Article 365 against such a recalcitrant state. Sir Ivor Jennings characterised the DPSP as 'Pious Aspiration' and also questioned the utility of importing into India of the 19th century an English philosophy of Fabian Socialism without the Socialism. Granville Austin considers these directives to be 'aimed at furthering the goals of the social revolution'. Besides the Directives contained in Part IV, there are certain other Directives addressed to the state in other parts of the Constitution. Article 350A enjoins every state and every local authority within the state to provide adequate facilities for instruction in the mother-tongue at the primary stage of education. Article 351 enjoins the promotion of the spread of the Hindi language. These instructions are not part of the DPSP but carry the same value.