What is the mental-chemistry approach to association? How does it relate to the idea that the mind is like a machine?
Mental-chemistry approach is the combining of ideas, and then analyzing them. Association is the primitive name for learning. New psychology comprises the combing of simple ideas into complex ideas and then analyzing them.
A clock or a machine can be disassembled and then reassembled to study its components. In the same way, this could be done with the mind. The study of mind included the study of its smaller units that govern the human nature. It ranges from intelligence to emotions, and other feelings.
Locke treated the mind like a machine just like the body was treated like a machine. The simple ideas are the atoms, in the Galileo and Newton world and are the units, which make up the mental being. These elements could be brought together, to arrange more complex structures.
This theory of association when applied to mind caused the mind to behave like a machine. John Stuart Mill also contributed to psychology, by suggesting the possibility of undertaking scientific study of the mind. Mill had given this statement, when Combe had rejected the idea of mind getting examined by scientific approaches. He suggested a new branch of psychology called ethology.