What is Literacy?

I view literacy as a tool for communication. I feel that communication and therefore literacy has four parts: reading, writing, speaking, listening. In my experience as a teacher I have found that you need all four aspects to be considered literate by the world. However, the question I am often asking is “Is one part more important than the other?”

What if there is a Deaf child that cannot hear or speak (they use ASL to communicate at school and home). But imagine if that child also cannot read or write. What are the implications of not being able to complete any of the four tasks I have listed as a part of literacy? The implications are major...to the extent of being isolated in your own world and therefore not literate.
What does this all mean....if there are four parts of literacy: reading, writing, listening, and speaking then which is the most important? Is it more important to be able to read than to speak? To listen rather than write? This is the question I ask because on a daily basis I work with a child that essentially cannot read or write and he is 12 years old. Yet he cannot speak fluent sentences either. Most of his sentences are three words long, and they are not usually grammatically correct. He can listen, but he doesn't always understand and you have to talk to him in five word utterances. So, is this child literate? No, not in my opinion. But what skill do I target? Do I try to teach him to talk correctly so that he can be understood and have his wants/needs met? Do I teach him to read so he can fill out medical forms, or a job application? Do I teach him to write so he can pay his bills? Most people would say that you should teach all of the skills...and I agree and do teach them. But is there one skill that has dominance over the others? You tell me...