It's been over fifty years since OO was invented. What it is? Do we know? Can we define it? Or is it just a phrase we used to mean "good". Are objects dead? Or will they live on as an important software paradigm? And how do objects fit into Functional Programming? In this talk Uncle Bob goes back over the history of how and why OO was invented, the claims that were made about it and the reality of what we finally realized. He'll discuss how OO is beneficial today, and why it will continue to be important into the future. In the end, he'll present an unambiguous definition that will likely surprise you, and show you why objects will be a primary organizing principle of software for the next several decades at least.