Introduction
Article 15(4) was inserted into the Constitution by way of amendment and wasn’t a clause which was present in the Constitution, since it came into being. This amendment gave the executive powers to make any special provisions for the advancement of any socially and educationally backward classes of citizens or for the Schedule Castes and Schedule Tribes. This provision was considered necessary by the legislature as India gained independence and a democratic form of Government came into being, the need to uplift the down-trodden was felt. Reservation were to be implemented initially for only 10 years but have being continuing till now.
Over the years the extent to which reservations should be allowed has been a matter of great controversy and has been discussed in various cases. The present condition is that reservations in general should not exceed 50%. But this was not always the position.
Since Article 15(4) permits discrimination in reverse by reserving seats in educational institutions, the extent of such reservation assumes great importance for the citizen, for the public generally and for the State.
An instructive illustration of such appointments to unreserved and reserved posts is furnished by the facts of T. Devadasan v. Union of India and Anr. Out of 45 appointments to be made, 16 were made from unreserved seats and 29 from candidates belonging to the Schedule Castes and Tribes. The petitioner complained that although he had obtained 61 per cent marks in the competitive examination, he was not chosen, whereas the percentage of marks secured by some out of the 29 candidates from reserved category was as low as 29. The petitioner would naturally feel a deep sense of resentment and injustice at being passed over in favour of candidates who had secured 29% marks and who were logically speaking not comparable to him. The injury to the public is that they have to deal with less able public servants. The injury to the state is a less efficient public service, and the blame which Govt. must shoulder for the shortcomings and blunders of its servants. These facts do not disappear because it is said that redress a great historical wrong done to a section of society the individual must put up with the feeling of resentment and injustice, and the public and the State must put up with a less efficient public service - at least for a reasonable time. But these evils make it imperative to ascertain the extent to which they must be tolerated.
The rationale behind the Supreme Court in determining the extent of reservations in several cases is discussed elaborately in the course this project.

Exception v. Illustration debate
It is common knowledge that an exception cannot eat up the general rule. Till the case of State of Kerala and Anr. v. N.M. Thomas and Ors. , Supreme Court decisions on Articles 15(4) and 16(4) had held that these articles were exceptions and that, speaking generally reservations should be less than 50%. Otherwise the exception would eat up the general rule. Against this uniform trend of authority there was Subba Rao J.’s dissent in T. Devadasan v. Union of India and Anr. There the majority opinion was that Article 16(4) was an exception and reservation therefore should not be greater than 50%. Subba Rao J. held that Article 16(4) was not an exception, and reservations could be greater than 50%.
Theory of Legislative Device
Subba Rao J. in T. Devadasan v. Union of India and Anr. propounded a theory which can be described as the theory of “legislative device” as a result of which according to him reservations could exceed 50% if the need be. Krishna Iyer J. adopted this theory in State of Kerala and Anr. v. N.M. Thomas and Ors. and quoted the following passage from the judgement of Subba Rao J. in T. Devadasan v. Union of India and Anr. which actually was a dissenting opinion. “The expression ‘nothing in this article’ is a legislative device to express its intention in a most emphatic way that the power conferred thereunder is not limited in any way by the main provision but falls outside it. It has not really carved out an exception, but has preserved a power untrammelled by the other provisions of the Article”.
The theory of Legislative Device basically interprets the words ‘nothing in this article’ differently. According to this theory by using these words the legislature used them as a device to confer a power upon Articles 15(4) and 16(4) which is untrammelled by other provisions of the Articles.
Thus, Krishna Iyer J. in- State of Kerala and Anr. v. N.M. Thomas and Ors. uses the theory of ‘legislative device’ propounded by Subba Rao J. to hold that Articles 15(4) and 16(4) were not exceptions but illustrations by their own self. Thus Krishna Iyer J. holds in State of Kerala and Anr. v. N.M. Thomas and Ors. that reservations can exceed 50% if need so arises. The reasoning which he provides is that Article 15(4) and 16(4) are not exceptions to the first clause but illustrations

Criticisms of the theory of Legislative Device
The theory of Legislative Device is untenable for reasons enumerated below:
a. “It ignore the scheme of Article 15 and 16 , and, more particularly, the relation of clauses (1) and (2) of Article 15 and 16, to clauses (3) and (4) of Article 15 and to clauses (3), (4) and (5) of Article 16 respectively.
b. It ignores the fact that the words “nothing in this article” appear as the opening words not only in Article 16(4) but also Article 15(3) and (4) and in Article 16(3) and (5) and in those four sub-clauses the opening words are not a legislative device.
c. It ignores the fact that it is impossible to argue that clauses (3) and (4) of Article 15 and clause (3) and (5) of Article 16 were inserted ex majore cautela.
d. It ignores the legislative history of Article 16(4) which shows that Article 16(4) was an exception to Article 16(1)
e. It ignores decisions of high authority which show that the words “nothing in this Act” or “nothing in this Article” are apt words for introducing an exception.
f. When the passage propounding the theory of legislative device is examined it will be found that it is difficult to give the words in the passage a rational meaning, and at any rate the theory leads to absurd results.”
The theory later on was abandoned by Krishna Iyer J. in Akhil Bharatiya Soshit Karamchari Sangh (Railway) v. Union of India and Ors. and it was accepted by him that Article 16(4) was indeed an exception to Article 16(1) and (2).
Sub-Article 15(1) and (4) are parts of Article 15 which appears under the group heading “Right to equality”. A plain reading of Sub-Articles 15(1) and (2) shows that they confer fundamental rights. Article 15(1) confers a fundamental right on every citizen by commanding the State not to discriminate against any citizen on grounds only of religion, race, caste, sex, place of birth or any of them. Article 15(2) is directed not only to the State but also to any person, and it provides that no citizen shall, on the prohibited grounds, be subject to any disability, liability, restriction or condition with regard to the matters set out in sub-clauses (a) and (b) of Article 15(2). Thus Articles 15(1) and (2) constitute legally enforceable fundamental rights. Article 15(3) does not confer any right, much less a fundamental right, on women and children, but merely confers a discretionary power on the State to make special provisions for them. Article 15(4), with which we are directly concerned, again confers no right, much less a fundamental right, on any socially and educationally backward class of citizens or on the Schedule Castes and Schedule Tribes, but merely confers a discretionary power on the State to make any special provision for the advancement of the aforesaid classes.
Thus as Articles 15(4) is more of an enabling provision which vests the State with the authority to make special provisions and 15(1) and (2) are legally enforceable fundamental rights. An enabling provision cannot be given primacy over a fundamental right. Allowing reservations to exceed 50% would mean giving primacy to Article 15(4) over 15(1), even if Article 15(4) was taken to be an illustration of Article 15(1) rather than an exception.