Aquinas argued that the observable order of causation is not self-explanatory. It can only be accounted for by the existence of a first cause; this first cause, however, must not be considered simply as the first in a series of continuing causes, but rather as first cause in the sense of being the cause for the whole series of observable causes.
So, says Aquinas, everything must have a cause, except the "first" cause, which must then be present in everything.
Is it too whacky to claim that the universality of Buddhist soteriology, as well as their denial of God and atman, is powered by an intuition that the end of a causal series is already present?
In the same way that a pitcher of water is already void before we empty it.
I'll put another, hopefully clearer way.
'Cause' is contained in 'effect' [everything is caused] but 'effect' is not contained in 'cause' [a causal series can be snuffed out]: if we call the root cause of our discontinuous illusions "ignorance", the cause of suffering, then wouldn't that mean it, ignorance, is already both present [samsara] and absent [nirvana] from moment to moment: that the end of conditioned suffering is now?