I think individualism is an illusion.
Every person is individual in the same sense that a cell is individual within the body. However, just as a cell will eventually die if you cut it away from the body, an individual will die as he or she is cut off from society.
The greatest punishment that we can conceive is to be isolated and left alone. That is why solitary confinement is used in prison to punish those who are being punished.
Humans are interdependent with one another. We rely on each other for resources, protection, support, etc. and we are reliant on our environment to provide for us.