I like to continue this. Empathy is not only positive (love/cooperation). empathy can also be negative (hate/competition).
Lack of empathy as in a psychopath means lack of positive empathy (but there is still negative empathy).
lack of empathy as in an autistic asperger means lack of both positive&negative empathy.
lack of both positive&negative empathy does not cause competition, it causes blindness for both cooperation & competition.
Detach yourself from word empathy and simply substitute word value. Word empathy has several different meanings, so any time I mention empathy anywhere I've noticed people have propensity to disagree based on what they understand it means. There isn't an agreement on what empathy exactly is so you can get stuck in this discussion forever. So lets use word "value". Say there is a value scale from 1 to 10 where 1 corresponds to giving a human being almost no value and 10 would correspond to giving human being a lot of value. In this case pure T corresponds to 1 and pure F corresponds to 10. Most people however use a combination of both functions. Thinkers use more T and Feelers use more F.
Empathy if you take it to mean just simple understanding of emotions does not require having F function really. You can use logic, sensing, intuition to coldly and rationally understand emotions of others and even predict them from what they say or their body language and facial expressions.
In case of Asperger's I read these people are not able to 'read' mental state of others and body language. I don't think this has to do with MBTI, but some sort of rather serious 'glitch' that happened in their mind (it has a genetic linker for it too). I wouldn't use MBTI to describe such kind of disorders.
So Viche:
What about people who take themselves down to take the other down? ( e.g. borderline women), how would you type them? What is their primary function?
They are certainly not thinkers!
In case of personality disorders I would not use MBTI to describe those. Right tools for the right job. And MBTI is not the tool that has been designed to explain significant mental disbalance. It is a tool that has been designed to let average people to find a good career fit. There is a danger of taking it too far to try to explain every single little thing in its light. Besides MBTI there is a ton of other psychological literature and other systems/models for human behavior some of which specifically address personality disorders.
However I do know of an article that tries to correlate personality disorders to functions, specifically exaggerated use of either the introverted set or the extraverted set. Borderline disorder is prescribed to having very strong Te and Ne and very weak Fi and Si (basically to highly extraverted ENFPs and ESTJs would exhibit borderline-like behavior). For INTPs heavy usage of Ti and Si is said to lead to Schizotypal personality disorder (same as for ISFJs). Reference:
http://personalitycafe.com/articles/25205-dominant-tertiary-loops-common-personality-disorders.html
You are also confusing actual ability to think with what is called "thinker" in MBTI. Function T doesn't give you the actual ability to think, it only places a certain slant on your thinking process. Nomenclature is sadly confusing and it leads people to believe that feelers go around without having thoughts in their head.
There are people who hate everybody, they think a lot about others, they hate them so much, they will make compromises to their own selfish rational interest, just take those damn "motherfuckers" down
They are certainly not thinkers!
Each function brings certain strengths to the way person is thinking, but because there exist these strengths there also exist weaknesses. Ever heard of the Tom Waits lyrics that go "If I exorcise my devils, well my angels may leave too". There is a lot of truth to that quote.