freefall68 wrote:What is Buddhism's take on deep sleep? Is there a consciousness during deep sleep when no mental formations are there for support?
That's a very interesting question. In order to maintain a degree of continuity between waking hours, different lifetimes, and to support the Abhidhammic notion of one moment of consciousness being dependent upon the former, the commentarial Theravada tradition came up with this bridging notion of bhavanga-citta.
Bhavanga-citta: 'subconsciousness' bhavanga-citta is a kamma-resultant state of consciousness vipāka, and that, in birth as a human or in higher forms of existence, it is always the result of good, or advantageous kamma kusala-kamma-vipāka, though in varying degrees of strength see: patisandhi, end of the article. The same holds true for rebirth consciousness patisandhi and death consciousness cuti, which are only particular manifestations of subconsciousness. In Vis.M XIV it is said:
As soon as rebirth-consciousness in the embryo at the time of conception has ceased, there arises a similar subconsciousness with exactly the same object, following immediately upon rebirth-consciousness and being the result of this or that kamma intentional action done in a former birth and remembered there at the moment before death. And again a further similar state of subconsciousness arises. Now, as long as no other consciousness arises to interrupt the continuity of the life-stream, so long the life-stream, like the flow of a river, rises in the same way again and again, even during dreamless sleep and at other times. In this way one has to understand the continuous arising of those states of consciousness in the life-stream. Cf. viññāna-kicca
Source: http://www.dhammawiki.com/index.php?tit ... anga-citta
However, bhavanga-citta doesn't appear in the suttas, because consciousness as taught by the Buddha is instead like what Walpola Rahula described in your earlier quote. [reposted here on account of the split topic]
Then the Buddha went on to explain consciousness in detail: 'Consciousness is
named according to whatever condition through which it arises: on account of the
eye and visible forms arises a consciousness, and it is called visual consciousness; on
account of ear and sounds arises a consciousness, and it is called auditory
consciousness; on account of nose and odour arises a consciousness, and it is called
olfactory consciousness; on account of tongue and tastes arises a consciousness, and it
is called gustatory consciousness; on account of body and tangible objects arises a
consciousness, and it is called tactile consciousness; on account of the mind and
mind-objects (ideas and thoughts) arises a consciousness, and it is called mental
The Buddha declared in unequivocal terms that consciousness depends on
matter, sensation, perception and mental formations, and that it cannot exist
independently from them. He says: 'Consciousness may exist having matter as it
means, matter as its object, matter as its support, and seeking delight it may grow,
increase and develop; or consciousness may exist having sensation as it means… or
perception as it means… or mental formation as it means, mental formation as its
object, mental formation as its support, and seeking delight it may grow, increase
freefall68 wrote:I ask this question because the issue of deep sleep consciousness is given lot of emphasis in advaita system. When I get up in the morning and declare that "I had a nice sleep", is it not my direct knowledge?
Such a comment would likely be based on factors such as your memory of any disturbances that were experienced during the night, and how your refreshed or otherwise you feel upon waking. Both of those factors relate to what is experienced.
On the other hand bhavanga-citta doesn't in any way relate to what is experienced via the six sense-media, and thus by the Buddha's definition (in contradistiction to the broader Theravada school) has no right to be regarded as citta, yet it is critical to upholding the structural continuity of the Abhidhammic framework. The Buddha of the Sutta Pitaka on the other hand expressed no interest in viññāna-kicca (functions of consciousness), having no need for scholastic models of transmigration and continuity.