Which part of the Indian Constitution deals with the concept of Welfare State? 

The correct answer is Directive Principles.

Key Points 
 Directive Principles of state policy are about establishing social and economic democracy in the state.

• These are some basic principles or instructions or guidelines for the government while formulating laws/policies of the country and in executing them.
• Directive Principles aim at the establishment of welfare states.
• Indian Constitution  Part IV tells about DPSP.
• The concept of DPSP is taken from Irish Constitution
• It is not justiciable in court.
• Dr. B.R Ambedkar called it "the novel feature of Indian Constitution". 

​Additional Information

• Fundamental rights are the basic human rights enshrined in the constitution of India in Part III
  • Fundamental rights are justiciable in court.
  • The idea of fundamental rights taken from the US constitution
• The idea of Fundamental Duties is inspired by the Constitution of Russia.
  • These were incorporated in Part IV-A of the Constitution by the 42nd Constitutional Amendment Act, 1976 on the recommendations of the Swaran Singh Committee.
  • Originally 10 in number, one more duty was added through the 86th Constitutional Amendment Act, 2002. All the eleven duties are listed in Article 51-A of the Constitution (the sole Article in Part-IV-A).
  • However, like the Directive Principles, the duties are also non-justiciable in nature.
• The Preamble was taken from the US constitution
  • Source of the authority of the constitution: It derives its authority from the people of India
  • Nature of Indian state: It declares India to be a sovereign, socialistic, secular democratic, and republican polity
  • Objectives of the constitution: It specifies justice, liberty, equality, and fraternity as the objectives
  • Date of adoption: Nov 26th, 1949.