Philosophy of mind
After behaviorism failed, materialist philosophers invented type physicalism. These philosophers thought that, if mental states are something material, but not behavioral, then mental states are probably identical to a brain states. In very simplified terms: For example, the mental state "desire for a cup of coffee" is actually just the "firing of certain neurons in certain brain regions". However, other philosophers saw that type physicalism could not explain an idea called multiple realizability. Multiple realizability means that a mental state can be created by different brain states. For example, a dog has a different brain and nervous system for a person. However, both can experience the mental state of "pain". This view led to a different kind of monism called functionalism, and compared the mind to a computer. Many functionalists think the mind is like software, and the brain is hardware.