[1][2] Considered to be the most prominent Western historian of Sikhism, his publications had introduced higher criticism to Sikh sources for the first time and influenced generations of scholars.
[3][4][5] However, his scholarship remains controversial among traditional Khalsa scholars, who accuse him of disrespecting the religion and argue that Sikhism can't be studied using Western methodologies.
[7][1] McLeod enrolled for theological studies at the Knox College and in 1958, joined the New Zealand Presbyterian Church, apparently out of a desire to serve the less privileged.
[1] In 1963, he enrolled for a PhD at the School of Oriental and African Studies under Arthur Llewellyn Basham and returned two years later upon a successful completion.
[5] In 1986, McLeod was chosen to deliver a series of public lectures on religion, sponsored by the American Council of Learned Societies (ACLS).
[5] In his PhD thesis (later published by OUP), McLeod introduced the tools of higher criticism and philology to Sikh janamsakhis and concluded them to have little reliable information.
[3] Simon Digby, for the Indian Economic and Social History Review, noted the work to be an important, rich, and rigorous study.
[11] A review in Archiv Orientální found his work to be the product of painstaking research and responsible approach, supplying a wealth of information on Nanak.
[13] Christopher Shackle notes that McLeod's questioning the historicity of previously unchallenged "facts" created a predictable ruffle among orthodox Sikhs.
[14][b] However, the work had exhibited a naive reductionist understanding of the links between hagiography and historical biography, and created a dead-end for scholars not willing to align with the Khalsa-centric school.
[3] Published a year before Guru Nanak's fifth birth-centenary, McLeod ran contrary to the "reverential and even hagiographical tone" of volumes that had flooded the market and his textualist methodology "transformed" the field.
[5][16] Christopher Shackle, in a review for Journal of the Royal Asiatic Society, found the work to be formidable in its pioneer borrowing of higher criticism from Biblical studies; it was far more sophisticated than his 1968 volume and was among the rare examples of major scholarship arising out of traditionally neglected areas.
[5][23] Clive Dewey was effusive in his praise of the work; even if McLeod had written nothing else, this "bravura performance" was sufficient to establish his unprecedented caliber in the field of Sikh Studies.
[25] Shackle found the second essay to be the "most stimulating", where McLeod used newer evidence to convincingly reject the popularly ascribed roles of Islam in development of Sikhism.
[28] Christopher Shackle, in a review for Journal of the Royal Asiatic Society, found the work to cement McLeod's reputation as the preeminent scholar of Sikh Studies.
[34] In a review for Nova Religio, George Adams noted an exhaustive examination of all important aspects of the Sikh tradition in a lucid and convincing manner.