In the Suttas, the arising of sensory-consciousness is said to be dependent upon the meeting of one of the six sense-organs (salayatana) and its corresponding object. The process of seeing, for example, is described as a conditional process where “dependent on eye and visible forms, eye-consciousness arises” (SN 12.43). Without the presence of the appropriate sense organ (e.g., the eye) or the corresponding object of reference (e.g., rock), sensory-consciousness (e.g., eye-consciousness) cannot arise.
Furthermore, dependent co-arising specifically states, “From the arising of name-and-form comes the arising of consciousness. From the cessation of name-and-form comes the cessation of consciousness.” Additionally, in DN 15, special attention is paid to the complex relationship between name-and-form (nama-rupa), i.e., mentality-materiality, and consciousness (vinnana)—with the Buddha detailing the mutual dependency of mental and physical activity and consciousness.
In one analogy used to illustrate their relationship, consciousness and name-and-form act as two sheaves of reeds leaning against one another. In essence, the two sheaves of reeds support one another, and if one were pulled away, the other would fall (SN 12.67). Therefore, it is clear that sensory-consciousness is a dependently existing phenomena that cannot exist without a sense organ or its corresponding object of reference.
As for the nature of consciousness itself, however, I cannot say for sure. Perhaps consciounsess is something that is fundamental to the basic structure of the universe; perhaps consciousness is purely a conditional phenomenon with nothing else underlying it; perhaps there is a separate type of consciousness that does not partake of any of the six senses or their objects—for me, the jury is still out on this one.
In terms of the aggregate of consciousness (vinnana-khandha), it is clear that consciousness is a dependently existing phenomena … However, there are a couple of sutta passages which could seem to suggest that there is a form of consciousness that does not come under the aggregate of consciousness. For example, Thanissaro Bhikkhu states in a note to his tranlsation of MN 109, “One form of consciousness apparently does not come under the aggregate of consciousness. This type of consciousness is termed vinnanam anidassanam — consciousness without a surface, or consciousness without feature. MN 49 says specifically that this consciousness does not partake of the “allness of the all,” the “all” being conterminous with the five aggregates.
The standard definition of the aggregate of consciousness states that this aggregate includes all consciousness, “past, present, or future… near or far.” However, because vinnanam anidassanam stands outside of space and time it would not be covered by these terms. Similarly, where SN 22.97 says that no consciousness is eternal, “eternal” is a concept that applies only within the dimension of time, and thus would not apply to this form of consciousness.”
While this view that there is a type of consciousness that lies outside of space and time, and therefore, outside the consciousness-aggregate altogether is not a view that is supported by the “classical” Theravada Tradition in which the enitre Tipitaka and its commentaries are considered authoritative, the imagery of consciousness that “does not land or increase” mentioned in SN 12.64 does seem to support such a possibilty, even if some might say that comparing this imagery of consciousness that “does not land or grow” to the consciousness of Nibbana is taking it out of context. At least I think so.
But the commentaries gloss the term “vinnanam anidassanam” in a way that denies such a possibilty. Using the Kevatta Sutta (DN 11), for example, Suan Lu Zaw, a Burmese lay-teacher of Pali and Abhidhamma, explains that according the the Kevatta Sutta Atthakatha [DN 11 commentary], vinnanam does not refer to the usual meaning of “consciousness” here, but instead defines it as, “There, to be known specifically, so (it is) “vinnanam“. This is the name of Nibbana.” He also explains that the following line of DN 11, “Here (in Nibbana), nama as well as rupa cease without remainder. By ceasing of conscousness, nama as well as rupa ceases here” illustrates this point. He states that, “Nibbana does not become a sort of consciousness just because one of the Pali names happens to be vinnanam.”
And finally, he concludes by using a quote from a section of the Dhammapada Attakatha [Dhammapada commentary], which apparently states that there is no consciousness component in parinibbana after the death of an arahant. This, of course, is in direct contrast to Thanissaro Bhikkhu’s note to this particular sutta which suggests that this term refers to a consciousness that lies outside of space and time, and therefore, outside the consciousness-aggregate altogether. Basically, what this controversy boils down to is the experience of Nibbana and the nature of that experience.
The general tendency is to either describe Nibbana as the ending of all consciousness, all awareness, or in other words, to stress the cessation aspect of Nibbana, or to describe Nibbana as a state of purified awareness, “consciousness without feature”, or in other words, to stress the transcendent aspect of Nibbana. The “classical” Theravada Tradition favors the former view of Nibbana while others, like the Thai Forest Tradition, favor the latter.
That being said, rebirth is essentially renewal of existence. As with most Eastern philosophies and religions, Buddhism does not view death as the final end of phenomena. In Buddhism, only Nibbana is said to be the final end of phenomena in regards to the arising and passing away of beings (AN 10.58). According to the teachings on dependent origination, if there are sufficient conditions present, those conditions with inevitably result in future births (SN 12.35). Along with consciousness, craving (tahna) plays a vital role in the renewal of beings and the production of future births. To illustrate how craving could result in future births, the Buddha used a simile in which he compared the sustenance of a flame to that of a being at the time of death. Essentially, a flame burns in dependence on its fuel, and that fuel sustains it. When a flame burns in dependence on wood, for example, the wood sustains that flame.
However, when a flame is swept up and carried away by the wind, the fuel of wind sustains that flame until it lands upon a new source of fuel. In the same way, a being at the time of death has the fuel of craving as its sustenance (SN 44.9). The last consciousness of a being at the time of death, with the presence of craving, is the cause for the arising of a new consciousness. In the human realm, this would be in combination with the union of a healthy sperm and egg, although the Buddha often mentioned various other forms of birth in other realms of existence—none of which are free from suffering. Hence, the Buddha states, “Wherever there is a basis for consciousness, there is support for the establishing of consciousness. When consciousness is established and has come to growth, there is the production of renewed existence” (SN 12.38). The Buddha never really got more specific than that, though.
Finally, to remove one of the more common misunderstandings in regard to consciousness, in response to the view that “it is this same consciousness that runs and wanders through the round of rebirths, not another” put forth by Sati, a bhikkhu that was the son of a fisherman, the Buddha rebukingly said, “Misguided man, have I not stated in many ways consciousness to be dependently arisen, since without a condition there is no origination of consciousness” (MN 38). This eliminates the idea of consciousness as “self.” Coming back to the teachings on rebirth, the “re” implies that something happens again, and that something is birth, i.e., the appearance of the aggregates, which takes place again and again. As such, this process of birth, death, birth, et cetera will continue as long as the requsite conditions are present. The word for “rebirth” in Pali is punabhava, which literally means “re-becoming” or “renewed existence.”
Although the aggregates are impermament, they are conditioned by causes anterior to birth, and act as causes for future births. Kamma is what makes entire this process possible. In Bhikkhu Bodhi’s words, “When ignorance and craving underlie our stream of consciousness, our volitional actions of body, speech, and mind become forces with the capacity to produce results, and of the results they produce the most significant is the renewal of the stream of consciousness following death” (Anicca Vata Sankhara). Therefore, while there is a type of continuity invloved in this process, it should not be mistaken for something substantial. As such, this “stream of consciousnes” should not be understood as a static thing, but simply a complex and uninterupted process of arising and ceasing in which both consciousness and craving play an important role. The term “rebirth” is merely a convenience.