A common-sense type argument put forward by J.S. Mill tries to show that because I know that my body is responsible for certain sensations – such as pain and pleasure – I know how this causes me to react. Therefore, when I see other people who possess the same type of bodies as myself, and I see that they react to certain experiences in similar ways, I can guess that they are experiencing similar things. In other words, I use my own knowledge of how my own inner states take place as an analogy of how others’ mental states arise.

Look at the following diagrams:

Me

Someone Else

As you can see, when I observe myself, there are 3 parts to my experience: a physical stimulus, a mental realisation and a physical reaction. However, when I consider other people, only 2 of these components are available to me: the initial stimulus and the reaction. However, because I know that I react in the same way as others do to similar experiences and I seem to possess the same bodies as them, I can fill in the missing box. Or can I?