Describing the external impact of dissenting opinions,Chief Justice Hughes famously said: “A dissent in a Court of last resort is an appeal . . . to the intelligence of a future day, when a later decision may possibly correct the error into which the dissenting judge believes the court to have been betrayed.”
A classic example of an opinion “appealing to the intelligence of a future day” is Justice Benjamin Curtis’s dissent from the US Supreme Court’s now notorious,1857 decision in Dred Scott v. Sandford.  The Court held, 7-2, in Dred Scott that people of African descent whose ancestors were brought to the United States as slaves could never become citizens of the country. Accordingly, an African American could not invoke a federal court’s diversity-of-citizenship jurisdiction in a free State to assert his freedom from slavery.
Justice Curtis disagreed in an opinion remarkable for its time. At the founding of USA as a Nation, he wrote, African Americans were “citizens of at least five States, and so in every sense part of the people of the United States,”thus among those for whom and whose posterity the Constitution was ordained and established.”
A further example is the Justice Harlan’s dissent, in the Civil Rights Cases The Court, in that 1883 decision, by 8-1, invalidated a federal law entitling “citizens of every race and color” to the “full and equal enjoyment” of modes of transportation and places of public accommodation. Justice Harlan the lone dissenter wrote
If the Thirteenth and Fourteenth Amendments are to be enforced “according to the intent with which . . . they were adopted,” “there cannot be, in this republic, any class of human beings in practical subjection to another class.”
Today we view equality as an quintessential principle.
Dissents of this order, Justice Scalia rightly commented, “augment rather than diminish the prestige of the Court.” He explained: “When history demonstrates that one of the Court’s decisions has been a truly horrendous mistake, it is comforting . . . to look back and realize that at least some of the [J]ustices saw the danger clearly and gave voice, often eloquent voice, to their concern.”
In Indian judicial history there are many dissents but one  that i would like to put before , was ,by Justice Mudholkar and Justice Hidayatullah.
Now in keshavanada Bharati case 7-6, by a razor thin majority , basic structure doctrine was given to test the amending power. And it was held that Parliament could amend any part of the Constitution but cannot alter or amend the basic structure or essential features of constitution.
Today it sounds appealing to be a common-sense perspective but it was not for the judiciary back in those days , it was a question broached upon for years and was at last put to rest in the aforementioned case.
Let me give a brief context to as to why I say so,
In Sankari Prasad v. Union of India, 1952 the Constitution
(First Amendment) Act, 1951 was challenged on a number of grounds,one of them being that “law” in Art 13 (2) includes “constituent law” and since the amendment in question abridged the fundamental right under Art 31, it was unconstitutional and void. The Court described the argument as “attractive” but held unanimously that“law” in Art 13 (2) did not take in an amendment; it was only a
restriction on the legislature in regard to ordinary laws and not in respect of constituent laws, there being a well-recognized distinction between ordinary law and constituent law.
It was also held that Parliament had power to amend every provision of the Constitution including the provisions of Part III and that such power was derived from Art 368 itself.
This stood as law for almost14 years until,
In Sajjan Singh v. State of Rajasthan,1965 the Constitution (Seventeenth Amendment) Act, 1964, was sought to be held invalid. The petitioners were affected by one or the other Act added to the Ninth Schedule by the Constitution(Seventeenth Amendment) Act. Petitioners urged the Court to reconsider the correctness of the Sankari Prasad decision in so far as it held that Parliament had the power to amend Part III of the Constitution. The Court declined to do so but thought fit to comment on that decision.As regards Article 13(2) three of the five judges, including the
learned Chief Justice Ganjedargadkar, observed:
it would be unreasonable to hold that the word ‘law’ in Art 13 (2)takes in Constitution Amendment Acts passed under Art 368.
Hidayatullah and Mudholkar, JJ, delivered as a minority view, separate judgements expressing their doubts on the merits of the reasons given by the majority judges. Justice Mudholkar took the view that the amending process in Art 368 is itself a legislative one, and if it is so,law,in Art 13 (2) would embrace even a constituent law.
J Mudholkar wrote:
The result of a legislative action of a legislature cannot be other than law,
and therefore, it seems to me that the fact that the legislation deals with the amendment of a provision of the Constitution would not make the result any the less a ’law‘.
The matter stood in this state for 2 year till 27th February 1967, when the Supreme Court rendered a decision in Golak Nath v State of punjab,1967 reopening the question of Parliament’s power to amend Part III of the Constitution, namely, the conflict between the majority and the minority in Sajjan Singh’s case” and the ’’great importance of the question raised”
The Court, comprising all eleven judges of the SupremeCourt, was sharply divided on the interpretation of Art 13 (2)and Art 368. The majority of six judges overruled the decision in the Sankari Prasad and held that “law” in Art 13 (2) includes a constitutional amendment because ’’amendment cannot be made otherwise than by following the legislative process.
The conclusion reached by majority was
Amendment is “law” within the meaning of Art 13 of the Constitution, and therefore, if it takes away or abridges the rights conferred by Part III thereof, it is void.
As a result of the Golak Nath decision, Art 13 (2) had become an impervious rock of prohibition against the State and any amendment of the fundamental rights so as to take away or abridge them had become a legal impossibility.
This dissent by 2 judges Justice Mudholkar and Justice Hidayatullah disguised as minority view ,rebelling with majority ,at that time is remarkable in itself, as it paved the way in Golak Nath’s decision which in some way laid the foundation in the Keshavanada Bharati case though the term law in article 13 was held to exclude an amendment of constitution made under Article 368. And upheld the 24th Amendment Act 1971 which inserted Clause 4 in article 13 and Clause (3) in article 368.
Now coming to the recent judgement in State of Punjab v Davinder singh
A seven-judge Constitution bench headed by Chief Justice Chandrachud, by a majority of 6:1, set aside five-judge bench verdict of 2004 in the EV Chinnaiah vs State of Andhra Pradesh case which had held that no sub-classification of Scheduled Castes (SCs) can be allowed as they are a homogeneous class in themselves.
Overruling the Chinnaiah verdict,It said:
“The state can sub-classify, inter alia, based on inadequate representation of certain castes. However, the state must establish that the inadequacy of representation of a caste/group is because of its backwardness,”
Except for Justice Bela M.Trivedi, the other five judges concurred with the findings of the CJI.
Justice Trivedi, in her 85-page dissenting judgement, said it is only Parliament which can include a caste in the SC list or exclude it, and states are not empowered to tinker with it. The Scheduled castes, she ruled, are a “homogeneous class” incapable of being sub-classified further.
Why is this dissent so important?
It is so because it points out the inconsistency and the flaw in the majority  opinion, 
under Article 341 and 342 of constitution it expressly mentions only president can notify the SC and ST hence the parliament. Not the governor of a state.
Thus, In conclusion as Justice Rohinton F Nariman, said:
“Dissent in a Court of last resort is an appeal to brooding spirit of the law and to the intelligence of the future day and ultimately this dissent what it is ,molds it into law”.