The Four Temperaments originated in ancient times, and were known as the 'four humours'.
It was believed that your personality was determined by the balance of black bile, phlegm, yellow bile, and blood in your body, which is how the temperaments get their archaic and rather gory-sounding names.
This is, as we know now, pure rubbish; our bodily juices don't determine who we are.
However, while they were wrong about the cause, the observations about personalities do still hold some value.
It's sort of like how the Ancient Egyptians believed that the sun rose because it was rolled into the sky by a giant invisible dung beetle. The fact that they were wrong about the beetle bit doesn't mean that the sun doesn't rise.
Their knowledge of the sun's journey was detailed and accurate enough that they could use sundails and make calendars. Just because they were dead wrong about the cause doesn't mean that their knowledge of the effect was wrong too.
The temperaments are a way of classifying peoples' emotional attitudes, the foundations of their personality. They apply in a very broad strokes way - that is, they are vague rather than specific and detailed - and make no attempt to identify every detail of a person's personality.
They are words like 'mammal' or 'reptile', not words like 'dog' or 'rattlesnake'.
'Personality' and 'temperament' are not synonymous. Temperaments are merely one of many facets of a person's overall personality.
Two people may have identical temperaments, but could be completely different in every other way.
Many works of fiction will in fact have a Hero and a Villain who have identical temperaments, but who could never be said to be similar people.
They are easily recognised, once you know the patterns; you needn't know a person for longer than five minutes in order to at least get an idea of their temperaments.
This is like how you can tell whether someone's male or female at a glance, usually. Knowing their gender will give you an idea about their personality, but it won't come close to showing you every detail about them.
Similarly, two women will technically share the same anatomy, which is why they can be classed together as 'women', but they will differ in every detail. The sizes and shapes of their parts set them apart as individuals, in the same way that two people of the same temperaments will be set apart as individuals by the intensity of their temperamental traits.
As humans, we all have access to a wide spectrum of different emotions. We all get angry, happy, sad, and so on. We all wish at times to be around others, or to be alone. The temperaments are determined by the balance of these emotions.
For example, the choleric temperament is more prone to anger than the other temperaments. However, we all get angry from time to time. Being angry and being choleric are NOT synonymous. If you are angry, it does not mean that you are 'being choleric right now'. If you are angered easily and frequently, however, then THAT is probably a sign that you are choleric.
There are only four temperaments, but that's a very limiting number, so it's more useful to describe people in terms of temperament blends.
These blends consist of a primary and secondary temperament, such as MelancholicPhlegmatic or CholericSanguine. The order is important; a MelancholicPhlegmatic blend is noticeably different to a PhlegmaticMelancholic one.
The primary temperament describes the most obvious part of a person's personality, while the secondary one just serves to flesh it out in more detail.
They're called 'blends' and not 'pairs' for a reason. A MelancholicCholeric person does not have a 'melancholic half' and a 'choleric half', as if inhabited by two different people.
This is like how purple light is made up of red and blue, but it can't be said to have a 'red side' or to be 'blue sometimes'. The blended colour is distinct from both blue and red and neither can be isolated, despite it being made from them both.
Temperaments are not passing moods, or phases in our attitudes. They are the foundation of our emotional natures, which stay constant throughout life (barring perhaps severe brain injury), from birth until death, even though every other aspect of our personality may change.
Remember, temperaments are only one of many facets of a person's personality!
This is like how - as a fully grown adult - you may build muscles, get a tan, wear different clothes, get a different hairstyle, and so on, but your skeleton will not change through any of this; you won't grow any taller. You won't change sex or eye colour either.
Our views, our beliefs, our tastes, our confidence levels... All these things DO change while staying bound to a fundamental temperament. The temperament affects how these things change.
For example, if subjected to abuse, a choleric person might become aggressive towards others in order to express their built-up anger and to have control and dominance that they cannot have around their abuser. A phlegmatic person put through the same abuse might become self-destructive or catatonic. The same stimulus affects people in different ways due to their temperaments.
Temperaments are determined by nature, not nurture.
While you could get a vague idea of a person's interests or behaviour from their temperaments, they cannot be used to predict such things with any kind of certainty.
However, they can be used to understand *why* a person did a specific thing, and they determine their approach to a specific situation.
For example, in response to teasing, a phlegmatic person might retreat within themselves and cry, because they are shy, sensitive and submissive, while a choleric person might start a fight, as they are bold, domineering, proud, and aggressive.
Temperaments should be seen as 'wholes', rather than lists of parts. They can be described using traits, but they are not determined by traits.
You must connect the dots to see the bigger picture when determining temperament. You'll probably find that you have traits from them all, but only the overall description of two of them will fit.
All snow is white, but not everything that's white is snow.
Melancholics are sensitive, but being sensitive does not make you 'part melancholic'.
There's not really such a thing as a 'choleric trait'; the choleric temperament can be described using a list of traits, but a person is not 'part choleric' just because they have one single trait from that list.
Let's say you describe an animal using the following list of traits: 'pointed ears, long, fast legs, a long face, short fur, and a mane on its neck'.
From combining those traits into one *whole*, you'd get something like a horse.
However, taking one in isolation - say, 'pointy ears' - doesn't work; cats have pointy ears, but are not horses. Nor are they 'part horse' (ignoring biological shared ancestry), since the word 'horse' is not used in that way.
Similiarly, losing a leg doesn't make a horse into a different animal. Lacking a common trait of a temperament does not mean that you aren't that temperament if you do fit the 'whole picture'.
A common objection to the very idea of temperaments follows this form:
"People are too complex to be described with simple labels like this."
"That dog has pointed ears, so it's part horse... Oh, but it has paws, so it's part cat! Its fur is long; it's part bear! It has teeth; it's part lizard! It's part every animal, so it can't be defined within the confines of a single label! It is far too complex!"