This thread is kind of a gestalt of various theories I've posted around about the functions.
Please note, these are just my current theories (or maybe not, if I haven't updated in a while), none of these are set in stone. I welcome debate if you disagree.
There are 8 functions. They are divided into 4 Perceiving functions (which gather information), and 4 Judging functions (which determine what to do with the information). Perceiving then further divided into Sensing and iNtuition, both of which come in extroverted and introverted varieties. Likewise, Judging is divided into Feeling and Thinking.
Everyone uses all 8 functions, to varying degrees. It's the role (and not strength) that you use each function in that determines your type. Your type is determined by your primary and secondary function. Pi and Je are paired together, and Pe and Ji are paired together. For the record, I believe that IPs lead with a juding function, and IJs lead with a perceiving function.
A function is like a muscle, it is strengthened by using it, and atrophies when unused.
S - 5 senses data.
N - Ideas.
T - Objective Judging.
F - Subjective Judging.
Extroverted Functions - Linear.
Introverted Functions - Webbed.
Introverted functions store the fruits of their labor in memory.
Everything starts with perception. Each of the 4 perceiving functions interprets the data in a different way, and passes that on to the judging function, which then decided what to do with the information.
Pe gathers external data and gives it to Ji.
Pi also gathers external data, but also connects the data together. Compares new data to the model it has and gives that information to Je. It can also reevaluate data already collected.
Ji builds an internal model with building blocks acquired from Pe.
Je builds an external model with blueprints acquired from Pi.
Se - Gathers 5 senses data. Least amount of interpretation of any of the functions. Passes on "pure" information to Ji.
Si - Gathers 5 senses data. Connects that data to other data and stores that model. In this way, the present situation can remind and even transport the user into the past. Gives that model to Je to build externally.
Ne - Gathers external ideas and explores the possibilities. Follows the threads from one idea to new ones. Passes on these possibilities to Ji.
Ni - Gathers external ideas, and discovers the connections to other stored ideas. Leads to "mystical insights" into how one idea leads to another. Gives model to Je to build externally.
Ti - Uses building blocks from Pe to build a model of the universe. Evaluates each piece of data, and determines where it belongs.
Te - Uses blueprints provided by Pi to recreate internal model in the external world using objective methods.
Fi - Uses building blocks from Pe to build a model of the universe. Evaluates each piece of data according to how it makes one feel emotionally, and constructs a value system.
Fe - Uses blueprints provided by Pi to recreate internal model in the external world using external value system. Adopts a group and their values and uses those values as a criterion.
Instead of retyping stuff, I'll just link this thread:
Thread where I write about function stuff.
The effects of this:
IPs can be just as stubborn as EJs, due to leading with a judging function. However, IPs gather data externally, which can help offset this, but that internal model can be hard to break.
TiNe and Ni can appear very similiar. Both develop internal connections between ideas. Difference is that Ni discovers the connections, Ti makes them. Ti's connections are more "real". Also, Je is very obviously differrent from Ne. Also, I suspect this (along with this) is why many people think INTPs have Ni.
T isn't inherently logical, instead it takes the object and it's qualities, without assigning subjective judgment.
Ne and Ni are effectively the same process, just applied either externally or internally, which is why Ns are differentiated more by T/F. The same does not hold true for Se and Si, and N/S is the most different, which is why you get SJ, SP, NF, and NT.
E/I is determined by how much focus you place on your E or I functions.
Pi can gather data externally or internally.
Fi is logical. But instead of dealing with objective data, it deals with subjective, ie, how it makes you feel. Otherwise, it functions essentially the same as Ti. I suspect this is why many IFPs have trouble typing themselves.
Ts and Emotions:
(hoo boy, getting real deep in theoretical territory here)
Emotions are reactions meant to motivate you away from negative situations, and towards positive situations.
Their primary purpose is survival.
Ts, being more objective, are less effected by emotions because they have learned (perhaps subconsciously) that it is more effective to not act on their emotions.
However, everyone has emotions. Emotions must be expressed, otherwise they will express themselves.
Emotions can only be expressed if these conditions are met.
1. The emotion is known.
2. The emotion is understood.
3. There is an empathic connection.
In actuality, the person only has to believe there is an empathic connection, even if the other person (or object, or even yourself) won't understand.
So um... ya. More to come later, maybe.