Who is Hindu is the question to be answered convincingly. Let us first examine the word Hindu and wherefrom it came. Let us not go into deep discussion and in unnecessary debate. It is a proved fact that the word Hindu derived from Sindhu – the River, the historic local name for the so-called Indus River in the north-western part of Bharat. The foreigners who came to India had to cross the River Sindhu and they named the people who lived on the other bank of the River Sindhu as Hindu and also they pronounced Sindhu as Hindu. This is the reason that Bharat had been named as India and the people are Hindus. Anyhow, one good thing happened in this accidental name that is they treated all who live on the bank of Sindhu as Hindus. They did not find any difference in the groups that lived here in Bharat. Thus, the foreigners perceived Unity in Diversity at the first instance they entered Bharat.
Now let us examine legal validity or scope of this term – Hindu as per Constitution or Law. Though the Indian Constitution does not mention any thing about Hindu or who is Hindu or what is Hinduism, it certainly talks about to whom the word Hindu means.
Constitution of India Status on Hindu – Article 25 in the Constitution of India 194925. Freedom of conscience and free profession, practice and propagation of religion (1) Subject to public order, morality and health and to the other provisions of this Part, all persons are equally entitled to freedom of conscience and the right freely to profess, practice and propagate religion
(2) Nothing in this article shall affect the operation of any existing law or prevent the State from making any law (a) Regulating or restricting any economic, financial, political or other secular activity which may be associated with religious practice; (b) Providing for social welfare and reform or the throwing open of Hindu religious institutions of a public character to all classes and sections of Hindus
Explanation I The wearing and carrying of Kirpans shall be deemed to be included in the profession of the Sikh religion
Explanation II In sub clause (b) of clause reference to Hindus shall be construed as including a reference to persons professing the Sikh, Jaina or Buddhist religion, and the reference to Hindu religious institutions shall be construed accordingly
In Hindu Marriage Act, the Law categorically says that this Act applies,- (a) To any person who is a Hindu by religion in any of its forms or developments, including a Virashaiva, a Lingayat or a follower of the Brahmo, Prarthana or Arya Samaj; (b) To any person who is a Buddhist, Jaina or Sikh by religion, and (c) To any other person domiciled in the territories to which this Act extends who is not a Muslim, Christian, Parsi or Jew by religion, unless it is proved that any such person would not have been governed by the Hindu law or by any custom or usage as part of that law in respect of any of the matters dealt with herein if this Act had not been passed. Explanation. - The following persons are Hindus, Buddhists, Jainas or Sikhs by religion, as the case may be,- (a) Any child, legitimate or illegitimate, both of whose parents are Hindus, Buddhists, Jainas or Sikhs by religion; (b) Any child, legitimate or illegitimate, one of whose parents is a Hindu, Buddhist Jaina or Sikh by religion and who is brought up as a member of tribe, community, group or family to which such parents belongs or belonged; and (c) Any person who is a convert or re-convert to the Hindus, Buddhist, Jaina or Sikh religion. (2) Notwithstanding anything contained in sub-section (1), nothing contained in this Act shall apply to the members of any Scheduled Tribe within the meaning of clause (25) of Article 366 of the Constitution unless the Central Government, by notification in the Official Gazette, otherwise directs. (3) The expression "Hindus" in any portion of this Act shall be construed as if it included a person who, though not a Hindu by religion is, nevertheless, a person whom this Act applies by virtue of the provisions contained in this section. Now let us understand the Constitutional validity of the term Hindu or Hinduism.
Constitution explicitly says that Sikhs, Jains and Buddhists are included in Hindu Religion and they are treated as Hindus. Nobody claimed or said that they are not Hindus. Though the Constitution raises a question whether these three religions are included under Hindu or not and answers the query that they are Hindus.
Further, the Constitution clearly uses the term Religion to mention Sikhs, Jains, Buddhists and Hindus. It means that the Constitution treats these sects as Religious Sects.
Now let us understand the Hindu Marriage Act as approved by our Constitution.
This Act clearly mentions to whom this Act applies
This Act applies to a person who is Hindu by any form of its sub-sects i.e. Sikhs, Jains, Buddhists, Veerasaiva, Lingayat, a follower of the Brahmo, Prarthana or Arya Samaj.
Furthermore, the Constitution says indirectly (rather more directly) who are not Hindus i.e. Muslim, Christian, Parsi or Jew by religion are not Hindus. This could be interpreted by the clause that this Act extends who is not a Muslim, Christian, Parsi or Jew by religion, unless it is proved that any such person would not have been governed by the Hindu law or by any custom or usage as part of that law in respect of any of the matters dealt with herein if this Act had not been passed.
This Act says that this Hindu Marriage Act applies to a person who is a convert or re-convert to the Hindus, Buddhist, Jaina or Sikh religion. It means that the persons who are converted to Hinduism, Jainism, Buddhist and Sikhism are treated as Hindus and the reconverted to these religions are also treated as Hindus.
Having examined the Constitution and Hindu Marriage Act, one can safely interpret that the following are Hindus as per Constitution and Hindu Marriage Act:
Persons domiciled in the territories to which this Act extends are Hindus meaning the Native Tribes of India
Jains, Buddhists and Sikhs are Hindus
Converted to 1 and 2 above are Hindus
Re-convert to 1 and 2 above are Hindus
Who are Not Hindus? The following are not Hindus as per Constitution and Hindu Marriage Act:
Any person domiciled in the territories and who is a Muslim, Christian, Parsi and Jew by religion is not a Hindu.
Now, let us consider the views of our Tradition and Shastras on the issue who is a Hindu.