That's the heart of what I believe. Even identical twins are different in some ways; for everybody, there never has (and never will be) another person the same.
However there are similarities between certain people. Not just in physical appearance, but in the way they are. They way the behave. How they relate, and learn, and make decisions. And to understand others better - to help our own communication and relationships - it can be valuable to learn from those who have researched and observed and produced theories to explain the patterns.
One of the oldest is the theory of temperament. Ancient Greeks divided people according to which body fluid of four they thought was most prevalent. Over the ages there have been quite a few similar theories about what motivates people at their core, the most recent in this genre being Keirsey's temperament theory. His book '' Please Understand Me II" is well-written and appealing in many ways. It divides the entire world into just four temperaments:
- The Idealist who seeks authenticity and rapport
- The Artisan who seeks freedom and impact
- The Rational who seeks achievement and competence
- The Guardian who seeks belonging and security.
Another problem is that within each of these four temperaments there are huge variations. Two are explained by Keirsey. Each temperament has those who are 'Introverted' or 'Responding', and those who are 'Extraverted' or 'Initiating'. Extraverts gain their energy from other people, Introverts become drained by other people.
The other division is into Role-informing or Role-directing: if we want someone to do something, we have a preference either for asking them directly, or for giving them some pertinent information.
So four temperaments divided twice leads to sixteen possibilities; these are - mostly - congruent to the well-known Myers-Briggs types.
Of course nobody (or hardly anybody) finds their type by taking a questionnaire, of which there are several online and some available professionally. Answers depend on how we interpret the questions, how honest we are, what mood we're in when answering the questions, and possibly what we think the questions are leading to. When I first came across Myers-Briggs, I seemed to test as ISTJ. An Introverted Guardian with role-directing style. The descriptions I found online (there are many) all seemed to be reasonable, although I prided myself in being rather different - more thoughtful, less rigid, not remotely interested in business or commerce.
Then I started studying cognitive functions - the way some of the functions of Myers-Briggs operate within each of us. It became clear that ISTJ was not correct, and I considered ISFJ. Later on, in discussing temperament, I realised INFJ is more likely still.
But INFJ isn't all of who I am. There are other personality models - many of them. I've learned a bit about the Enneagram, which deals more in motivation than behaviour. No doubt there are many others, and more will be discovered. None of them, to my way of thinking, is the whole truth. Each one is simply a different way of looking at humanity, seeing different patterns. Like a kaleidoscope. Or a single thread in a tapestry. Or the construction of a certain model from Lego pieces, which can be taken apart and re-built in a completely different way. If one model helps me understand someone better, or learn how to communicate with them better, then I'll adopt it for a while. If it doesn't help with a particular problem, I'll try something else.