[1] He believed that the credibility of Christianity depended on its ability to relate to Buddhism, which was the faith of the majority of the Sri Lankan population.
[1][4][3] His findings eventually led to his most popular work, the book titled Buddhism: Beliefs and Practices in Sri Lanka (de Silva 1974).
[6] In Tilakkhana, or the three characteristics – anicca, dukkha and anattā – of all existence discovered by the Buddha in his diagnosis of the human predicament, de Silva finds the appropriate starting point for such a theology.
In his search for Tilakkhana in the Bible, de Silva finds anicca and dukkha in a number of Biblical passages, such as Psalms 90, that speak of the transitoriness, suffering, and anxiety of human life.
This leads him to believe that "the polarity of conflict between being and the possibility of non-being that lies at the core of human existence, the mood of anxiety, the finitude and precariousness of man's life, is a familiar theme that runs through the Bible.
Contrary to popular belief, de Silva shows that modern Christian scholarship does not support the notion of a soul as an immortal entity separate from the body.
[4][5][14] He argues that such a misconception arose as a consequence of the translation of the Bible into Greek: The idea of an immortal soul is certainly a firmly established traditional belief of Christians, but it is a belief that has entered Christian thinking through the influence of Greek Philosophy and is altogether alien to what the Bible teaches about the nature and destiny of man....
It can be confidently said that in the Bible, there is no notion of an immortal soul existing independently as an eternal, immutable, and perdurable entity, which inhabits the body and escapes it at death.
[15] Furthermore, Kitagawa argues that de Silva could have entertained the possibility that Theravada Buddhism might look for Ultimate Reality more readily in the Mahayana Buddhist tradition, rather than turning towards Christianity.
"[14] From the evangelical theologians, Tissa Weerasinghe believed that de Silva needs to put more emphasis on the "glaring disharmony" between Christianity and Buddhism that their differing views on the biblical notion of soul suggest.
[18] In a publication that aims at an evangelical approach to religions and cultures, Yung interprets de Silva's contribution as not so much an able exercise in dialogue, but, rather, a brilliant Christian apologetic, addressed to Theravada Buddhists.
[18] This, de Silva believes, is one of the "deepest dilemmas in Buddhism," leading him to ask the question "What is the self that denies the self and at the same time asserts that it alone can save the self?
By examining his own culture, de Silva goes on to show that the majority of lay Buddhists in Sri Lanka view the Buddha as a living saviour, who is able to confer blessings to mankind.
[22] In her Ph.D. thesis containing a chapter on de Silva's work, Damayanthi Niles claims that there is a problem with de Silva's argument in relation to salvation, in that it "reconciles the exclusive Christ-event and the inclusive vision of God's salvific plan purely on Christian terms," and that it does not take the "religious visions and commitments of other faiths seriously.
[4] With this frame of mind, de Silva studied the beliefs and practices of people with respect to death, such as the phenomenon of mediums, with help from Buddhist exponents of reincarnation.
Regarding Purgatory, de Silva states in this paper that the Hindu/Buddhist view, where Ultimate Reality is reached through a process of purification through liberation from self and elevation to stages of spiritual development, is more acceptable than the belief in a single life on earth and an everlasting hell or heaven after death.
The kind of "suffering" as a penalty for wrongs done, but as a painful surrender of the ego-centered self, the losing of self, the discovery that one is anattā in the process of finding one's true being.
Purgatory is a process of spiritual death and rebirth, of progressive sanctification, a process which begins in this very life.In his final Dialogue journal publication Reflections on Life in the Midst of Death, de Silva explains that it is sin which has created the illusion of self in man, and that it is this illusion that drives man towards self-possession and selfishness.