We say that each human is unique yet we constantly classify and categorize individuals. Why do we this and what information might we use to classify/categorize people?
What are the advantages and disadvantages of categorizing individuals
Although each human being is unique in an absolute sense, just as each cat, snowflake, mosquito, or leaf is an absolute singular unique individual, each object, whether human or not, has characteristics that it holds in common with other individuals. In fact, to say that a given entity is "human" is to place it in category, just as to say that an entity is a "cat" also places it in a category. In fact, for a description of an object to be meaningful, it must include general terms.
Imagine I were to describe person ABC you had not met by saying "ABC looks like XYX". If you have not met XYZ, this is useless information. If I say that ABC belongs to familiar categories to you such as "woman", "elderly", "Shia Muslim", "widow", "wealthy", etc, you get a much better picture of her. Also when we study people to predict, for example, their risk of getting certain diseases, how they are likely to vote, etc. we need to divide them into categories to use statistical data. Overgeneralizing, by assuming that people who belong to one category (e.g. Muslim) also belong to unrelated categories (terrorist, philanthropist) leads us to make bad judgements. Some people who belong to the category Muslim (and many who do not) are terrorists and some who belong to the category Muslim are philanthropists and some are not.
Carl Jung, the famous Swiss psychiatrist, wrote a book titled Psychological Types in which he traces the history of attempts to categorize people from all the way back to the ancient Greeks. He offers his own scheme of categorization, which has become the one most commonly accepted. Jung was the man who coined the terms "introvert" and "extravert." The widely used Myers-Briggs Type Indicator is based strictly on Jung's theories. You can take a modified version of the test yourself without charge by looking for Myers-Briggs Type Indicator test on the web. You can also click on the reference link below to access information about it in eNotes.
Jung divided people into eight basic categories. The Myers-Briggs Type Indicator has something like fourteen categories. The main purpose of that assessment is to assist people in finding which vocations are most suited to their psychological types. It is also used by employers in hiring and in placement. I personally believe that this test is of great potential value to people because it can help them find where they belong and possibly save them from the all-too-common fate of ending up in the wrong vocation. It should also be valuable to students in choosing their majors.