What is meant by, "The whole of a person is greater than and different from the sum of the parts"?

When we talk about the parts of a person what we are really talking about are the many facets people have that give us an idea of who they are, what they value, their beliefs, their personality even things like personal hygiene. But also and perhaps more so is the sum of their experiences and their reactions. But all of that combined is still less than their value as a human being.

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