Article 14 and 16 both are the part of equality code of Constitution. Article 14 guarantees equal protection of law to the people of India.
Article 16 embodies the fundamental guarantee that there shall be equality of opportunity for all citizens in matters relating to employment or appointment to any office under the State. Though enacted as a distinct and independent fundamental right because of its great importance as a principle ensuring equality of opportunity in public employment which is so vital to the building up of the new classless egalitarian society envisaged in the Constitution, Art. 16 is only an instance of the application of the concept of equality enshrined in Article 14.
In other words, Art. 14 is the genus while Art. 16 is a species. Article 16 gives effect to the doctrine of equality in all matters relating to public employment. The basic principle which, therefore, informs both Arts. 14 and 16 is equality and inhibition against discrimination. Now, what is the content and reach of this great equalising principle? It is a founding faith, to use the words of Bose, J., “a way of life”, and it must not be subjected to a narrow pedantic or lexicographic approach.
Equality is a dynamic concept with many aspects and dimensions and it cannot be “cribbed, cabined and confined” within traditional and doctrinaire limits.
From a positivistic point of view, EQUALITY IS ANTITHETIC TO ARBITRARINESS. In fact equality and arbitrariness are sworn enemies; one belongs to the rule of law in a republic while the other, to the whim and caprice of an absolute monarch. Where an act is arbitrary, it is implicit in it that it is unequal both according to political logic and constitutional law and is therefore violative of article 14, and if it affects any matter relating to public employment, it is also violative of art. 16.
Articles 14 and 16 strike at arbitrariness in State action and ensure fairness and equality of treatment. They require that State action must be based on valid relevant principles applicable alike to all similarly situate and it must not be guided by any extraneous or irrelevant considerations because that would be denial of equality.
Where the operative reason for State action, as distinguished from motive inducing from the antechamber of the mind, is not legitimate and relevant but is extraneous and outside the area of permissible considerations, it would amount to mala fide exercise of power and that is hit by Arts. 14 and 16. Mala fide exercise of power and arbitrariness are different lethal radiations emanating from the same vice: in fact the latter comprehends the former. Both are inhibited by Arts. 14 and 16.”
Govt. of Andhra Pradesh v. P.B. Vijaykumar
In the case of Govt. of Andhra Pradesh v. P.B. Vijaykumar and another, AIR 1995 SC 1648. It was observed thus:
“6. The interrelation between Articles 14, 15 and 16 has been considered in a number of cases by this Court. Art. 15 deals with every kind of State action in relation to the citizens of this country. Every sphere of activity of the State is controlled by Article 15(1). There is, therefore, no reason to exclude from the ambit of Article 15(1) employment under the State. At the same time Article 15(3) permits special provisions for women. Both Arts. 15(1) and 15(3) go together.
In addition to Art. 15(1) Art. 16(1), however, places certain additional prohibitions in respect of a specific area of State activity viz. employment under the State. These are in addition to the grounds of prohibition enumerated under Article 15(1) which are also included under Article 16(2). There are, however, certain specific provisions in connection with employment under the State under Article 16.
Article 16(3) permits the State to prescribe a requirement of residence within the State or Union Territory by parliamentary legislation; while Article 16(4) permits reservation of posts in favour of backward classes. Article 16(5) permits a law which may require a person to profess a particular religion or may require him to belong to a particular religious denomination, if he is the incumbent of an office in connection with the affairs of the religious or denominational institution.
Therefore, the prohibition against discrimination of the grounds set out in Article 16(2) in respect of any employment or office under the State is qualified by clauses 3,4 and 5 of Article 16. Therefore, in dealing with employment under the State, it has to bear in mind both Articles 15 and 16 ─ the former being a more general provision and the latter, a more specific provision.
Since Article 16 does not touch upon any special provision for women being made by the State, it cannot in any manner derogate from the power conferred upon the State in this connection under Article 15(3). This power conferred by Article 15(3) is wide enough to cover the entire range of State activity including employment under the State.”
The rule of parity
The rule of parity is the equal treatment of equals in equal circumstances. The rule of differentiation is enacting laws differentiating between different persons or things in different circumstances. The circumstances which govern one set of persons or objects may not necessarily be the same as those governing another set of persons or objects so that the question of unequal treatment does not really arise between persons governed by different conditions and different sets of circumstances.
The principle of equality does not mean that every law must have universal application for all persons who are not by nature, attainment or circumstances in the same position and the varying needs of different classes of persons require special treatment. The Legislature understands and appreciates the need of its own people, that its laws are directed to problems made manifest by experience and that its discriminations are based upon adequate grounds.
The rule of classification is not a natural and logical corollary of the rule of equality, but the rule of differentiation is inherent in the concept of equality. Equality means parity of treatment under parity of conditions. Equality does not connote absolute equality. A classification in order to be constitutional must rest upon distinctions that are substantial and not merely illusory. The test is whether it has a reasonable basis free from artificiality and arbitrariness embracing all and omitting none naturally falling into that category.
 E.P. Royappa v. State of Tamil Nadu and Another, AIR 1974 SC 555
 State of Kerala v. N.M. Thomas, (1976) 2 SCC 310