And then in the 1950s, philosophers hold this novel idea that perhaps the mind is just identical with the brain. OK? And this had occurred to philosophers before, and it so happen, it happened around the same time the first department of neuroscience started forming like MIT and Sandford so for. But basically, there is a couple of philosophers both educated here in Oxford Place and Smart, and they made the claim that the mind just is the brain. So that is the identity theory. And with identity, identity in logic is the strongest relation. When you have identity between A and B, you don't have two things, you have one thing. Alright? So now when you talk about mental events, you are talking about brain events. Maybe when you talk about brain events, you are talking about mental events. OK? So that's the identity theory. And it's very popular and it's basically the idea that mental properties are just properties of the brain.