The UPAYA is a “skillful means” by which Heaven seeks to win souls; since souls are in illusion, the “means” necessarily takes on something of the illusory, hence the diversity of doctrines, methods, and religions, or rather the incomparability of their various aspects. (GTUFS: FormSR, Truth and Presence)
Let us recall that in Buddhist terminology an UPAYA is a “celestial stratagem” meant to save us from the world of suffering, and which can vary according to the needs of men; its “truth” is not literal, it is primarily practical or efficient. (GTUFS: SurveyME, The Irrefutable Religion)
Let us recall that by UPAYA the Buddhists understand a “divine stratagem” or a “saving mirage”: it is not intrinsic truth that is of primary importance, but saving efficacy. (GTUFS: ChristIslam, Alternations in Semitic Monotheism)
If, on the one hand, it is as an UPAYA that the limitative dogma is given or accepted by Heaven, it is, on the other hand, because of its limitation that this UPAYA will be providentially contradicted by other UPAYAs: hence religious divergences, which are at once a scandal and a blessing. It is the limitlessness of Atma that necessitates the plurality of UPAYAs; every limit demands a repetition that completes it while apparently contradicting it. (GTUFS: LogicT, Evidence and Mystery)
We have had recourse more than once to the Buddhist notion of UPAYA, the “saving stratagem”: now an UPAYA, by the very fact that it is a means “sanctified by the end,” has a certain right to sacrifice the truth to opportunity; that is, it has this right to the extent that a given truth remains foreign to its own fundamental truth and to the corresponding spiritual strategy. An UPAYA, in order to be effective, must exclude; the way of “God as such” must exclude the way of “God become man” and conversely; but either way will retain a reflection of the other, the function of which will remain secondary. Islam, on pain of being ineffectual or something other than itself, must exclude the Christian dogma; Christianity for its part must exclude the characteristic axiom of Islam – as it excluded at the outset the axiom of Judaism, which in this connection coincides with that of Islam. The Epistles of Saint Paul show how the Apostle simplifies Mosaism with the intention of buttressing Christianity from the point of view of both doctrine and method; in an analogous manner, all that shocks Christians in Moslem imagery must be interpreted as a symbolism meant to clear the ground in view of the efficacy of the Muhammadan UPAYA. In order to understand a religion, it is useless to stop short at its extrinsic polemic; its fundamental intention lies in its intrinsic affirmation which testifies to God and leads to God. The imagery is nothing, the underlying geometry is everything. (GTUFS: SurveyME, Confessional Speculation: Intentions and Impasses)