In Buddhism we speak of three types of phenomena: First, there are evident|
phenomena that are perceived directly.
Second, there are slightly hidden phenomena, which are not accessible to
immediate perception. There are differences of opinion on this even within
Buddhist philosophy. Generally speaking, we think this second type of
phenomena can be known indirectly by inference.
One example of something known by inference is that anything arising in
dependence upon causes and conditions is itself subject to disintegration and
momentary change. This momentary change is not immediately evident to your
senses. You can look at something with your eyes, and it does not appear to
be changing right now, but by inference you can know that it is momentarily
changing. This is an example of the second category of phenomena.
Third, there are very concealed phenomena, which cannot be known by either
of the two preceding methods. They can be known only by relying upon
testimony of someone such as the Buddha.
-- "Consciousness at the Crossroads: Conversations with the Dalai Lama on
Brain Science and Buddhism", edited by Zara Houshmand, Robert B.
Livingston, and B. Alan Wallace, published by Snow Lion Publications