In the following passage—from Buddhahood Without Meditation (p. 111)—Dudjom Lingpa describes how sensory appearances are neither identical to nor completely separate from the ground of being (aka the nature of mind, aka Buddha-Nature, aka Pure Awareness), by using the metaphor of planets and stars reflected in a lake:
Because all phenomena of samsara and nirvana arise distinctly and individually within the expanse of the ground of being, or buddha nature, like the planets and stars reflected in a lake, it is free of the limitation of being identical to them. Because the modes of samsara and nirvana, however they arise, are of one taste with this same ground of being, or buddha nature—just as the planets and stars reflected in the ocean are none other than the ocean—it is free of the limitation of being separate from them.
Because conceptual mind tends to function by way of dualistic polarities, we think that things must be either “the same” or “different” from one another, in the strong sense of completely “separate” or totally “identical” to one another.
But the relationship between Pure Awareness and phenomena does not correspond in any way to this dualistic formulation. Pure Awareness is not identical to phenomena—in the same way that a lake (as a whole) is not identical to reflections of the planets and stars on its surface.
Why? Because reflections of planets and stars come and go, but the lake itself remains. Also, reflections have particular characteristics (e.g. shape, color) which—though they appear for a while on the surface of the lake—are not a permanent inherent quality of the lake itself.
To assume that the lake is identical to its reflections would be an unwarranted limitation upon the true nature of the lake itself—which is not dependent upon reflections. Similarly, to assume that Pure Awareness is identical to sensory phenomena would be to assign an unwarranted limitation to Pure Awareness, the ground of being.
Though Pure Awareness is not identical to sensory phenomena, neither is it completely separate from them—in the same way that a lake is not completely separate from reflections of planets and stars (when these are appearing on its surface).
Why? Because the reflections depend, for their appearance, upon the presence of the lake. If the lake and the reflections were completely separate from one another, then even if the lake disappeared completely, the reflections would continue to appear. But this is not how it is. Instead, every reflection bears the “one taste” of the lake itself.
To assume that the lake is completely separate from the reflections would be an unwarranted limitation upon the true nature of the lake—which has the capacity to display reflections. Similarly, to assume that Pure Awareness is completely separate from sensory phenomena would be to assign an unwarranted limitation upon Pure Awareness. Part of its unlimited nature is its capacity to appear in an unlimited array of forms.
A mind that is functioning dualistically assumes categories such as same/different and identical/separate to be mutually exclusive and mutually exhaustive. In other words, any and all phenomena (or in this case, pairs of phenomena) must fit neatly into one and only one of the two categories.
A gateway into knowingly abiding as Pure Awareness is to fully grok that the relationship between Pure Awareness and sensory phenomena does not fit into either of these conceptualized categories. The relationship can be defined neither in terms of absolute identity, nor in terms of absolute separation.
And yet, sensory phenomena continue to appear and disappear, arise and dissolve—within the “space” of Pure Awareness—completely free of any attempts to grasp them with such dualistic concepts.