The awareness belonging to Buddha, then, is free from construction. But what, positively, could such awareness be like?
The digests are concerned to eliminate a number of possible errors in thinking about awareness without construction. The first of these is the error of judging such awareness to be identical with simple unconsciousness, a simple absence of mental activity. If it were, such absence would be easy to attain: a sharp blow to the head produces unconsciousness; and there are various meditational practices that dispose of many kinds of mental activity at an early stage of the practice of the path. But it is obvious that the absence of constructive activity that characterizes Buddha’s awareness is not so easily attained. Neither is it the case, according to the digests, that Buddha’s awareness is epistemically, phenomenally, or soteriologically as uninteresting as deep sleep or a drunken stupor.
More interestingly, the digests also negate the idea that unconstructed awareness is to be identified with a much more exalted meditative state called the ‘attainment of cessation’ (nirodhasamapatti) or the ‘cessation of sensation and conceptualization’ (samjnaveditanirodha). This is a condition attained by complex and difficult meditational practice, a condition wherein there are no mental events of any kind. It is not death; but it is not distinguishable from death by any phenomenal properties. The only difference between the two is that the attainment of cessation can be emerged from, while death cannot (not, at least, without various complications caused by the need to take on a new body and the like, complications that need not detain us here).
Buddha’s construction-free awareness is distinct even from this exalted condition, and the digests put this in formal terms by denying that Buddha’s awareness could be identified with the attainment of cessation, because if it were it would not be an instance of awareness (jnana) at all, which its name requires it to be, for awareness cannot occur where there are no mental events of any kind. The point here is the simple logical one that awareness is a species of mental event, from which it follows that no instance of awareness can be identified with a condition in which there are no mental events.
[… The digests negate] the claim that this awareness comprises any volitional turning of the mind toward its objects (alambanabhisamskara). This is not the same as denying that Buddha’s awareness has content, or consists of events with phenomenal properties; it is simply a denial that the phenomenal properties of its apparent objects are, or can be, things with which it can be involved in a sustained and intentional way. In so far as what appears in the mind does so with phenomenal properties, those properties do not lead the Buddha-mind to fasten upon them, to follow after them, or to make judgments that a particular thing with particular properties is now being experienced.
For example, suppose Buddha sees a blue pot. One way of reading the negation described in the preceding paragraph is to say that Buddha has a spontaneous (that is, effortless, nonvolitional) moment of awareness (jnana) consisting of a mental object or image (alambana, nimitta) whose phenomenal properties (akara) consist of a complex list of things such as ‘transient-blue-pot-here-now’; in English such an occurrence is best described adverbially by saying that Buddha is appeared to transient-blue-pot-here-now-ly.
[… T]he important distinction between Buddha’s blue-pot awareness and mine is that Buddha neither does nor can judge that it is being appeared to blue-pot-ly, whereas I, other things being equal, inevitably do. Buddha, moreover, does not engage in the constructive activity of manipulating and massaging its mental images; it has no affective response to them, and, above all, no concern for their endurance, cessation, or repetition. The digests sometimes express this by saying that Buddha does not behave like an artist toward the objects of its awareness.[.]
[...] If, in order to have phenomenal properties or modes of appearance, awareness must be characterized by effortful acts of attention toward specific objects (as it certainly must in most instances of ordinary awareness), then it is proper to say that Buddha’s awareness is nirakara, ‘free from modes of appearance.’ But if possessing modes of appearance can be understood through the simile of reflections on the surface of a mirror, then it is reasonable to say that Buddha’s awareness does have them—for a mirror, like Buddha’s awareness, does not engage itself with or focus upon specific ‘reflectables’; it simply reflects, spontaneously, perfectly, and without distortion, everything that passes before it.
[...] The thrust of the digests toward presenting the Buddha as maximally great requires the scope of Buddha’s awareness to be maximized: if it is good to have unconstructed awareness, then the temporal and spatial range of this awareness cannot be restricted or limited in Buddha’s case: it must be, as the digests claim it to be, strictly universal in scope. Buddha must therefore be, in some important sense, omniscient[.]
[...] The digests generally agree that Buddha’s universal awareness is not brought about by causes, since this would entail its contingency: if the proper causes had not obtained, its universal awareness would not have obtained. And this cannot be correct: Buddha’s awareness has always (sada) and necessarily (avasyam) existed.
[… Many similar passages link] Buddha’s permanence closely with its salvific actions. The limitless and perfect salvific efficacy that Buddha, understood as maximally great, must necessarily possess, requires that Buddha be present and active everywhere and at all times. Hence, Buddha must be permanent, without beginning or end in time.
The digests thus refuse to predicate any temporal properties of Buddha considered in se. Buddha is not earlier or later than anything, not temporally related to anything in any way. All Buddha’s temporal properties are of the kind described in chapters four and five: seems to S to be P at t. Correlated with this refusal is a denial to Buddha of causal properties: Buddha is not caused to do anything, nor does Buddha cause any non-Buddha to do anything. Buddha is, metaphysically speaking, simply identical with all atemporal states of affairs.
Paul J. Griffiths, On Being Buddha: The Classical Doctrine of Buddhahood
Excerpt (starting p. 155):