we know that the Parliament is the law making authority and also has the power to amend the constitution but it is important for us to understand that the parliament cannot amend all the provisions of the constitution. this is is because of the basic structure doctrine.
The doctrine of basic structure is a judicial made doctrine. It is understood that this is not a part of the constitution of India and was propounded on 24th of April 1973 in the famous case Kesavananda Bharati Sripadagalvaru and Ors. v. State of Kerala and Anr. In this case, the term basic functions of the constitution were used. The term basic structure was used in the case of Minerva Mills Ltd. and Ors. vs Union Of India and Ors. Which was decide on 3st July 1980.
I support the basic structure doctrine because this doctrine is brought in with the intention that the power of the parliament to amend the constitution must be restricted and the fundamental idea of the constitution must not be allowed to be amended. It is understood that the basic features like equality, secularity, Judicial review, rule of law and etc are not only a part of the preamble or the fundamental rights but also the fundamental idea of the constitution makers behind the drafting of the constitution. Though all the contents of the basic structure are not declared on any document, various cases (Waman Rao And Ors vs Union Of India (Uoi) And Ors. , Indira Sawhney & Ors v. Union of India, and many other cases) give us an idea of what could be the contents of basic structure doctrine. The fundamental rights (Part 3) of the constitution must be restricted from being amended because it will result in being a thread to the basic principles of not only the constitution but also democracy and therefore, they can be amended to widen the scope but not narrow it down.
In my opinion if there is no restriction on the amending power of the constitution, then the parliament will have unlimited power. It may start amending all the provisions of the constitution. For example, if the parliament amends the constitution by removing the right to seek judicial review then it will stop the people from going to courts for relief and eventually the judiciary will loose complete power. This will indirectly lead to the supremacy of the parliament and not supremacy of law which is against the principle of rule of law. This gives an unfair opportunity to amend any provision of the constitution and the preamble. This may also lead to demolition of the basic idea of democracy which including equality and principles of separation of powers and rule of law. It is not only India but many other countries do not allow the parliament or legislature to amend the essential or basic features of their constitution.
It is important for us to remember that precedents are an important source of law. As explained in the cases, the doctrine of basic structure is a law and holds value even though it is not a part of the constitution or it is an unwritten doctrine.
 Kesavananda Bharati v. State of Kerala, (1973) 4 SCC 225: AIR 1973 SC 1461.
 Minerva Mills Ltd. v Union of India (1980) 3 SCC 625.
 Waman Rao And Ors vs Union Of India (Uoi) And Ors.(1981) 2 SCC 362, 1981 2 SCR 1
 Indira Sawhney & Ors v. Union of India AIR 1993 SC 477, 1992