Introduction of the two-nation theory: 1924 Akhand Bharat
The two-nation theory is the ideology that the primary identity and unifying denominator of Muslims in the Indian subcontinent is their religion, rather than their language or ethnicity, and therefore Indian Hindus and Muslims are two distinct nations regardless of commonalities.
The two-nation theory was a founding principle of the Pakistan Movement (i.e., the ideology of Pakistan as a Muslim nation-state in South Asia), and the partition of India in 1947.
The ideology that religion is the determining factor in defining the nationality of Indian Muslims was undertaken by Muhammad Ali Jinnah, who termed it as the awakening of Muslims for the creation of Pakistan.
It is also a source of inspiration to several Hindu nationalist organizations, with causes as varied as the redefinition of Indian Muslims as non-Indian foreigners and second-class citizens in India, the expulsion of all Muslims from India, the establishment of a legally Hindu state in India, prohibition of conversions to Islam, and the promotion of conversions or reconversions of Indian Muslims to Hinduism.
The Hindu Mahasabha leader Lala Lajpat Rai was one of the first persons to demand to bifurcate India by Muslim and non-Muslim populations. He wrote in The Tribune of 14 December 1924: Under my scheme, the Muslims will have four Muslim States:
(1) The Pathan Province or the North-West Frontier;
(2) Western Punjab
(3) Sindh and
(4) Eastern Bengal.
If there are small Muslim communities in any other part of India, sufficiently large to form a province, they should be similarly constituted. But it should be distinctly understood that this is not a united India. It means a clear partition of India into a Muslim India and a non-Muslim India.
There are varying interpretations of the two-nation theory, based on whether the two postulated nationalities can coexist in one territory or not, with radically different implications.
One interpretation argued for sovereign autonomy, including the right to secede, for Muslim-majority areas of the Indian subcontinent, but without any transfer of populations (i.e., Hindus and Muslims would continue to live together).
A different interpretation contends that Hindus and Muslims constitute "two distinct and frequently antagonistic ways of life and that therefore they cannot coexist in one nation."
In this version, a transfer of populations (i.e., the total removal of Hindus from Muslim-majority areas and the total removal of Muslims from Hindu-majority areas) was a desirable step towards a complete separation of two incompatible nations that "cannot coexist in a harmonious relationship."
Opposition to the theory has come from two sources. The first is the concept of a single Indian nation, of which Hindus and Muslims are two intertwined communities.
This is a founding principle of the modern, officially secular Republic of India. Even after the formation of Pakistan, debates on whether Muslims and Hindus are distinct nationalities or not continued in that country as well.
The second source of opposition is the concept that while Indians are not one nation, neither are the Muslims or Hindus of the subcontinent, and it is instead the relatively homogeneous provincial units of the subcontinent which are true nations and deserving of sovereignty; the Baloch has presented this view, Sindhi, and Pashtun sub-nationalities of Pakistan and the Assamese and Punjabi sub-nationalities of India.