While Absolute Reality and Relative Reality will be familiar, "Groundless Reality" may be less so. The position of Groundless Reality is that there is no foundation to our experience, neither external to the knower nor internal. The world we experience is not determined by the external world nor is it determined by our internal world. It is brought forth in our actions as living beings.
To give you a flavor of the Groundless Reality position: Right now I am communicating with you in language, and I ask: Where is the meaning? In Absolute Reality it would be found in the words on the page. In Relative Reality it would be found in the mental processes of the reader. However, if either the words on the page or the mental processes of the reader were to change, a different meaning would be brought forth. The meaning, then, cannot be said to reside in either one. Meaning is co-determined by both. (Even this illustration makes a cleavage in the world which, though consonant with the other two positions, is not a feature of Groundless Reality.)
This position is often confused with the Relative Reality position. Before moving on to a second illustration it may be useful to mention one significant difference. Relative Reality shares with the Objectivist strain of Absolute Reality the notion that there is an objective reality. Objectivists claim this reality is directly knowable, while Relativists claim that it cannot be known. Those who favor the Groundless Reality position differ from the other two in considering the question of the existence of such a reality operationally meaningless. Reality, for them, is an immediate and intimate experience, even though it is one for which no foundation is to be found.
Our second illustration is a simple experiment that undermines the commonsense understanding that our experience of color is determined by the wavelengths of light coming from an object. A white light beam and a red light beam are both focused on a screen giving it a pink color. If a hand is held in front of the white light, because it obstructs the while light with its own shape, we see a reddish shadow of a hand on the pink background. However, if the hand is held in front of the red light its shadow stands out in a sharp blue-green hue. We would have expected to see a whitish hand on the pink background. Indeed, taking a reading of the light in the blue-green shadow area will indicate that it is white. But that is not what we see.
While many visual illusions, such as those where the same length lines appear to be of different length, can be resolved by measurement, the blue-green hand shadow is not such a case. On the contrary, while the phenomenon can be understood, no ground can be found on which to resolve the question of the real color. For the Groundless Reality position, this is always the case. There is no ground to anything; it is groundlessness all the way down.
The disappearance of an absolute ground, in the move toward relativism, has a shadow side in that some react by sliding into nihilism, with an attendant despair (either catatonically quiet or violently raging). Historically, the groundless reality approach appears to have been hidden behind many layers of initiation. Within the Buddhist Mahayana tradition it is explicit that an understanding of "emptiness" (their term for groundlessness) needed to be tempered by the development of compassion.
An appealing aspect of Groundless Reality is that you are totally inside your experience. There is no outside to it. It wraps you like your skin. In this position, the word "reality" can only refer to your experience. Experience is all we have. We might have the ability to imagine ourselves outside our own experience (just as we can imagine unicorns) but we remain inside our experience as we do so. Both the strangeness and simplicity of living in Groundless Reality is nicely captured in the title of one of Francisco Varela's papers: "Laying Down A Path In Walking."
Humberto Maturana and Francisco Varela (1987) The Tree of Knowledge: The Biological Roots of Human Understanding, New Science Library, Boston.
Humberto Maturana (1988) "Reality: The Search for Objectivity or the Quest for a Compelling Argument" in The Irish Journal of Psychology, 9,1, 25-82.
Francisco Varela, Evan Thompson and Eleanor Rosch (1991) The Embodied Mind: Cognitive Science and Human Experience, MIT Press, Cambridge, Massachusetts.