I’m not sure what you mean by “internal bifurcation”, but I interpret the passages fairly straightforwardly. There are forms in the world, and there are beings with eyes, and somehow, when the eye makes the right kind of contact with the form, an episode of visual consciousness occurs. It’s not very detailed or sophisticated, and leaves much open to amendation by more sophistated accounts of the process. The same is true of the accounts of the other sense organs - including the mysterious “mano” that perceives forms that exist only in the mind.
From the practice point of view, the point is to recognize that unless these contacts occur, feeling (the experience of the perceived object as attractive of repulsive, pleasant or painful) can’t arise. And without feeling, there is no craving or attachment. The practices of sati - learning to attend to everything that is occuring within the scope of one’s awareness - and then samadhi - deepening absorption into states of detachment from all of these “sense” processes, including the mind-sense - can lead to states characterized by the cessation of all craving and attachment, and thus a release from dukkha in this very life.
Taking up the internal bifurcation question, though, the Buddha in several places suggests that the ordinary process of attachment within these streams of conditioned processes includes the construction of an “I” that is the supposed continuous subject of the arising and passing states. When there is attachment to a pleaurable plate of food, or to a pretty dress, or to a powerful station in life, there is also the concept of “my food” or “my dress” or “I am the king”. Somehow the cessation of attachment is codependent on the cessation so I-making and my-making, so hard to achieve cognition of everything experienced as not-self, is the same as the end of dukkha.
It would be useful to have a reference. My guess is that the meaning will probably depend on what is meant by “external” in the context of the sutta, and also what nama-rupa represents in the context of the sutta ( it seems to vary ).
In MN10, the Satipatthana Sutta, “external” appears to mean other people.
In MN140, the Dhatu-vibhanga Sutta, “external” appears to mean outside the body. “And what is the earth property? The earth property can be either internal or external. What is the internal earth property? Anything internal, within oneself…”
And of course “internal” and “external” are applied to the sense-bases, eg eye = internal, and form = external. Again this seems to mean internal and external to the body, given that eyes and ears etc are part of the body.
Yes, and it’s also interesting to see how the sense-bases are discussed in terms of the fetters, in the fourth frame of the Satipatthana Sutta ( MN10 ):
"How, monks, does a monk live contemplating mental objects in the mental objects of the six internal and the six external sense-bases?.. He knows the ear and sounds… the nose and smells… the tongue and flavors… the body and tactual objects… the mind and mental objects, and the fetter that arises dependent on both; he knows how the arising of the non-arisen fetter comes to be; he knows how the abandoning of the arisen fetter comes to be; and he knows how the non-arising in the future of the abandoned fetter comes to be."
Another difficulty I have with the “internal bifurcation” theory is that it seems to require that eye and form are concepts which arise in dependence upon eye-consciousness. This is the opposite to what the suttas actually describe, ie eye-consciousness arising in dependence upon eye and form.
So perception can be unreliable? Sure. But I don’t see how this detracts from my point. The suttas do consistently describe the internal sense bases in terms of the organs ( eg eye, ear, etc ) which are clearly part of the body. You could say “ability to see” instead of “eye”, but this process still begins with the biological eye - the brain/mind then processes the “raw data” from the physical sense organs, creating a mental model of the world.
Sure. My point is that the raw data originates with the physical sense organs, and that these sense organs are part of the body. That is why they are described as the internal sense bases, being inside the body, rather than outside them. So the “eye” is internal to the body, while form is external to it.
Not really, it’s based on experience. I know that if I cover my eyes, there is no visual data, and therefore nothing to see. I know that if I plug my ears, there is no auditory data, and therefore nothing to hear. And so on.
The point though is that in the suttas the internal sense-bases are described in terms of the the physical sense organs, which strongly suggests that “internal” here means inside the body - the same distinction which applies to form in MN140.
It would be useful to see some clear support from the suttas for the alternative interpretation, that of a purely internal bifurcation into internal and external.
The suttas I’ve referenced all seem to support the straightforward interpretation of inside and outside the body.