I'm not sure I have the full understanding of idealism and realism. However, the ongoing discussion somewhat made me think of The Matrix. In Matrix all reality is an illusion. We are comatose beings hooked onto brain simulators that create our experiences and what we perceive to be the real world. So there is reality that the mind perceives, or is made to perceive (Idealism?). Then there is reality, the truth, where we are comatose (Realism?)
There is a scene though where the character Cypher is eating a steak. He knows the steak is not real. He knows the Matrix is telling his mind that it is juicy and delicious. But the most important thing he has realized is that ignorance is bliss. If it looks like a steak, smells like a steak, tastes like a steak, it is a steak. Damn whatever true reality is. Perception is reality.
The brain's various centres are each designated for a specific function. The senses take cognition of the environment. The anthropological basis of the nervous system was to facilitate an interaction with the environment, based on the individual's awareness of being separate from the environment. All senses subserve the function of underlining a sense of discreteness. Touch, taste, sound, smell and vision are instruments of discrimination. The entity that integrates these inputs and collectively coordinates them as a subject is the assumed 'identity'. The coordinated output of separateness that the senses keep generating is ego.
The brain also provides a data bank that stores previous interactions with the environment. These are categorised and stored for reference in the bandwidths of likes and dislikes. The brain helps fragment awareness into the subjective 'self' and objective 'non-self' - the observed world. This split awareness is switched on continuously and both the 'self' and the 'non-self' are vital for each other's symbiotic existence. Ie both perceiver and perceived are vital for perception.
Our own identity relies on our ability to perceive our self as uniquely different and distanced from the environment
Question 1- if identity was based merely on a deep-rooted sense of discreteness that the senses generate, would a person, alone in a dark, quiet room - whose brain is not being fed with sensory inputs - consider himself as non-existent?
Question2- Without any sensory inputs can there be any data bank to draw ideas from?
Question 3- How would the "intelligent designer" be able to design intelligently without any databank to fall back on?
There is a scene though where the character Cypher is eating a steak. He knows the steak is not real. He knows the Matrix is telling his mind that it is juicy and delicious. But the most important thing he has realized is that ignorance is bliss. If it looks like a steak, smells like a steak, tastes like a steak, it is a steak. Damn whatever true reality is. Perception is reality.
What if due to some reason his steak is perceived to be taken away ? If perception is reality ignorance in this scene may not be perceived as very blissful :)
Question 1- if identity was based merely on a deep-rooted sense of discreteness that the senses generate, would a person, alone in a dark, quiet room - whose brain is not being fed with sensory inputs - consider himself as non-existent?
This person has a priori knowledge. That can't be nullified into non-existence so I would say he will not consider himself non-existent in a dark quiet room with no sense data. May be he will feel a little disoriented but that's about it. IMO.
Question2- Without any sensory inputs can there be any data bank to draw ideas from?
History "embedded" in DNA will serve as the data bank.
Question 3- How would the "intelligent designer" be able to design intelligently without any databank to fall back on?
True, but it would also mean we are getting stuck in an infinite regress and if we manage to get out of it, we might find the answer.