Families, in the late 17th century, played an important role in the development of children. Since Robinson Crusoe left his family at a relatively young age, he was unable to see that people cared for him on a daily basis. To be set free, a person is able to live on their own without being told what to do and when to do it, with the government being the exception in that you have to do what they tell you to do. Crusoe fails to set Friday free because, Friday is the closest thing to a brother he's had in about thirty years.
Crusoe resembles a big brother trying to teach a younger sibling how to talk or comprehend what's going on. He say's "Made it my business to teach him everything that as proper to make him speak, and understand me when I spake." Crusoe takes on the role of the big brother, and Friday takes on the role as the younger brother. Younger brothers usually look up to their big brothers and want to be just like them. I believe this is why Crusoe wants to teach Friday. It gives Crusoe the feeling of being greatly admired.
By the title character teaching Friday how to talk, this signifies that they are coming together more as a "family" and are able to be more productive and efficient together. Communication is a huge barrier, and by them developing common grounds they are able to understand where one another are coming from. This helped give complete understanding of each other.
Crusoe taught Friday to do more than just communicate, he taught him how to hunt and harvest food.
"And let me know that he thought I had much more labour upon me on his account than I had for my self; and that he would work the harder for me, if I would tell him what to do." (Page 156)
He taught Friday to do these things because he cared for him. He wanted Friday to be able to support himself in more than one way in case something was to happen to one of his food resources. It is an older brother's duty to teach