"Yes we can" isn't a naive mantra of a wishful "positive thinking" movement. It is a reply to all of the people who, throughout our lives, have told us, "No you can't." Start with the disabled, who, throughout their childhoods, receive so many messages about what they can't do. They not only have to overcome the disability, but also the people who judge them on the basis of their abilities, rather than their abilities. Then consider people who come from a low income family: they are told about all of the careers they will never have a chance for. Sometimes their parents will automatically assume that they can't succeed in the field of their interests, and the parents force them into "safe" occupations. Anyone who doesn't have very Anglo looks, a perfect body and a large inheritance coming is subjected to the constant messages with all of the reasons why "you can't." That is what "yes we can" is responding to.