First question that I would like to dwell upon is the possibility of a consciousness developing in the absence of senses. Can a kid born with all the five senses deficient ever develop a conscious?
In absence of all five senses the external world will be nonexistent for the mind. There won’t be any development of language or any meaning full communication of the mind with the external world. In such a circumstance development of a consciousness is impossibility. Language is a critical tool for the process of thinking and without language the consciousness will not be able to develop any construct or idea of either self or the external world.
More Intriguing will be the situation wherein the person looses all his senses at a later stage of life due to some accident. The question is what will happen to an already developed conscious if all senses are taken away from it?
In this case consciousness is already developed to a state that it can think and it already has a concept of self. More so it has a tool the tool of language which can allow formation of new thoughts.
If we remove all the senses then the person cannot see, hear, smell, feel or taste. In such a situation he will lose the sense of space and more so if he cannot even feel his breath then he will lose the sense of time. That is the component of ‘here’ and ‘now’ is removed from the existence. The question is whether the concept of ‘I’ can still survive. Such a person will soon lose the reference of where he/she is and how long it has passed since he entered this state. In my opinion the consciousness will start degrading and slowly end up in chaos.
This process however may not be immediate. It must be possible for some time for the mind to go with reference of past experiences and memory. The possibility of new thoughts and ideas are however is a very tricky question. He has the tool of language and he has retention in form of memory. Would it entail that the consciousness can still indulge in meaningful thinking. It is however uncertain that in absence of any new sensory inputs all thoughts being generated are more or less based on the past memories or new thoughts may also get generated.
Present knowledge of human brain has it that only 25% of the cerebral cortex is sensory and motor cortex; rest is something called association cortex. This is where the modern psychology believes that thoughts originate. A complex association of sensory inputs past memories and perhaps many other factor lead to creation of thoughts. Coming to philosophy this question was most intricately studied by Immanuel Kant. His book Critique of Pure Reason draws a detailed study of what is thought and what is its origin before dwelling further into what are the limitation of human thoughts. To start with, he refutes thoughts being a mere interplay of sensation. So he dwells into thoughts that would remain if all the sensations are removed, knowledge and thoughts that are independent of sensation, ‘a priory’. He has taken mathematics as ‘a priory’. Mathematical knowledge per say is not dependent on any sensation. So if it is not an association of sensation, it is a derivative of past memory.
I am not sure however how much time it would take for the consciousness to lose the time and space reference and to start degrading.
Update: In a discussion, a person mentioned Helen Keller, a special case of a deaf and blind child. In reality, Helen Keller suffered the disease that made her deaf and blind when she was 19 months old. Irrespective of her ‘inabilities,’ she became a well known author, political activist and a lecturer. She was the first deaf and blind person who gained a Bachelor of Arts Degree and she worked a lot for her anti-war convictions. The person suggested that Helen Keller is somehow an exception and she developed consciousness without being aided with the necessary senses. He also claimed that the senses of ‘smell’, ‘touch’, and ‘taste’ are not that important for human survival and hence, can be ignored.
Firstly, Helen Keller was certainly an exceptional lady, no less genius than Louis Braille himself. However, she certainly enjoyed the benefit of ‘language.’ She not only read, she wrote too, she was a well known author.
Secondly, the person completely ignored the importance of the other three senses, ‘smell’, ‘touch’, and ‘taste’. Each of these senses is very important for survival. Think about a child who cannot feel the touch, or pain. One may kill himself without even knowing that they were harming their own existence. I was just thinking about 1 “Pain teaches,” said her mother, Trish Gingras. “Pain protects. Pain can save you from a lot of bad things in life.”
It should also be noted that without the sense of ‘touch’, one cannot use the Braille script which was used by Helen Keller to read and to write.
In addition, I do not agree with Kant who said that mathematical knowledge is not dependent on any sensation, I feel that even to attain mathematical knowledge, one is dependent on his senses.