
David Keirsey has sold over 4 million copies of his book in the last 30 years. Please Understand Me remains, to this day, as the book that best defines each of the 16 personality types.
Temperaments
Keirsey’s major contribution to personality type was his classification of the 16 types into 4 distinct Temperaments. They are:
NT: Intuitive + Thinking
NF: Intuitive + Feeling
SP: Sensing + Perceiving
SJ: Sensing + Judging
Along with those combinations, he also named each temperament using an archetype. For example, NTs are the Rationals; NFs are the Idealists, SPs are the Artisans, and SJs are the Guardians. This helps us to generally understand the mindset and structure of the types in a way that just listing the 2 letters would never allow.

Temperaments are not new to Myers Briggs. However, the Keirsey model and the official MBTI model (called “Function Pairs”) are slightly different. The official MBTI model lists the temperaments in a different combination, instead opting for: NT, NF, SF, ST. This is a more straightforward approach to creating the temperaments, as it simply combines the 2 middle functions.
Keirsey opted to approach things differently. Instead of simply adding the 2nd and 3rd letters together in a uniform manner, for the Sensor types, he added the 2nd and 4th letters together.
When I discuss Temperaments, I am working from the Keirsey model.
Take the Keirsey Temperament Sorter here (its 70 questions).
The 16 types

The descriptions that are given in Please Understand Me are some of the most precise and wonderfully elegant writings that I have come across in studying Typology.
Here are a couple of examples:
“Here is the herald, the spirited bearer of tidings. But underneath this effervescent enthusiasm is a person fiercely dedicated to “meaning” in life. (page 74, the ENFP)
“INFP’s seek unity in their lives, unity of body and mind, emotions and intellect. They often have a subtle tragic motif running throughout their lives, but others seldom detect this inner minor key.” (page 176, the INFP)
“Inefficiency is especially rejected by ENTJs, and repetition of errors causes them to become impatient. For the ENTJ, there must always be a reason for doing anything, and people’s feelings usually are not sufficient reason. (page 178, ENTJ)
“INTJs need only to have a vague, intuitive impression of the unexpressed logic of a system to continue surely on their way. Things need only seem logical; this is entirely sufficient.” (page 181, the INTJ)
There are many more examples, but do yourself a favor and discover them in full when you buy this book after you finish this article.

How to Use in your Daily Life
As professional typologists or enthusiasts, something that naturally happens is trying to Type people in your daily life. I imagine it’s just like studying psychology–now you’re diagnosing everyone’s mental illnesses. What the temperaments allow you to do, instead of trying to memorize all 16 types, is to only think of 4 possible temperaments as a starting point.
It is much easier to start typing someone and think. “He sounds like an NF Type,” than it is to try and decipher an INFJ from an ENFP.
My Rating and Recommendation
I can solidly make the recommendation to read Please Understand Me as the 1st or 2nd book you read when starting your typological journey. I give this book a 95/100. It can benefit anybody for any application in their life. It does not take an expert nor someone with a psych background to enjoy the description of E vs. I; NT vs. NF; or INFJ vs. ESFP. It is probably one of the rare MBTI books that can be enjoyed across the entire spectrum of personality types.
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