Singh was a self-proclaimed agnostic, as the title of his 2011 book Agnostic Khushwant: There is no God explicitly revealed. He was particularly against organised religion. He was evidently inclined towards atheism, as he said, "One can be a saintly person without believed in God and a detestable villain believing in him. In my personalised religion, There Is No God!" He also once said, "I don't believe in rebirth or in reincarnation, in the day of judgement or in heaven or hell. I accept the finality of death." His last book The Good, The Bad and The Ridiculous was published in October 2013, following which he retired from writing. The book was his continued critique of religion and especially its practice in India, including the critique of the clergy and Priests. It earned a lot of acclaim in India, where such debates are rare.