I know the differences. I know that there are around a dozen (maybe more) users here on this site who are undecided. I am one of them.
"oh well I'm 50/50 S/N" <<
It's a recurring theme on this board and others.
Why do INTPs and ISTPs have to be different?
We are the Ti-doms.

It's been said that one way to quickly tell the difference is that ISTPs care about how things work - that is often the purpose of (our/their) logical analysis. To be interesting, the object of analysis must be practical and concrete. ISTPs use known data and facts to reach underlying principles. Is this where Ni comes into play?
So, do INTPs not care about how things work? Are (we/you/they) really just interested in theories for the sake of theory? Is this what makes (them/you/us) pure thinkers? INTPs can analyze anything, concrete or abstract? Is that it?
So let's talk about Se, then? It's so easy to work yourself into a never-ending loop:
Se notices the details in the environment and may lead to spontaneous action,
ISTPs have a tendency to conserve their energy, biding their time until they "sense" something that draws their attention, then they take action.
ISTPs have exceptional hand-eye coordination ... respond quickly and accurately in emergency situations, Se gives them a leg up on the physical world, talented athletes ...
But there are lots of examples of ISTPs who defy this and INTPs who defy (by proxy) it as well. Once again, we get nowhere. Most people are halfway in the middle.
It's a Bell Curve meets Venn Diagram situation and the probability that a given individual is not a "pure" type seems to be very high.
They say that the auxiliary function isn't really developed all that well until late adolescence? So until then, what? INTPs and ISTPs are too similar to differentiate? WE NEED STEREOTYPES people!
Then there's video typing - the end all. Or is it? Suddenly we can tell the difference between Ne and Se in thirty seconds by watching a person's eyes. Now there's "pure" INTPs and "mudblood" INTPs ... INTPs who actually aren't INTP because their eyes don't reflect TiNe. So what then? We're at the mercy of the video typing experts?
The oft' stated advice to newcomers is to perform a functional analysis of the self. Identify and understand the 8 cognitive functions and their respective polarities, learn how these correspond to the 16 MBTI types.
Ti-dom, check
Fe-inferior, double check
Ne, wtf is that?
Se, ...uhhhh check
Si, check, definitely!
wait ... contradiction already? OK, so NOT Se.
Te? sorta
Ni ... mayhaps
oh well let me just take the cognitive function test
It says I use Se and Si? hrmmm.
It also says I use Te and Ti.
INFJ? No ... wait, they're too rare. No, probably INFJ. Everybody is INFJ these days...
ISTP then! No ... Si (D'OH) Maybe I don't "get" Si.
How come every Si description available rings home then?
I must be Si-dom?
ISFJ then. ... well, no not really. That's not right... Can't I be TiSi? No? DAMMIT.
INTP then ... wait, no ...
"oh well I'm 50/50 S/N" <<

It's a recurring theme on this board and others.
Why do INTPs and ISTPs have to be different?
We are the Ti-doms.


It's been said that one way to quickly tell the difference is that ISTPs care about how things work - that is often the purpose of (our/their) logical analysis. To be interesting, the object of analysis must be practical and concrete. ISTPs use known data and facts to reach underlying principles. Is this where Ni comes into play?
So, do INTPs not care about how things work? Are (we/you/they) really just interested in theories for the sake of theory? Is this what makes (them/you/us) pure thinkers? INTPs can analyze anything, concrete or abstract? Is that it?
So let's talk about Se, then? It's so easy to work yourself into a never-ending loop:
Se notices the details in the environment and may lead to spontaneous action,
ISTPs have a tendency to conserve their energy, biding their time until they "sense" something that draws their attention, then they take action.
ISTPs have exceptional hand-eye coordination ... respond quickly and accurately in emergency situations, Se gives them a leg up on the physical world, talented athletes ...
But there are lots of examples of ISTPs who defy this and INTPs who defy (by proxy) it as well. Once again, we get nowhere. Most people are halfway in the middle.
It's a Bell Curve meets Venn Diagram situation and the probability that a given individual is not a "pure" type seems to be very high.
They say that the auxiliary function isn't really developed all that well until late adolescence? So until then, what? INTPs and ISTPs are too similar to differentiate? WE NEED STEREOTYPES people!
Then there's video typing - the end all. Or is it? Suddenly we can tell the difference between Ne and Se in thirty seconds by watching a person's eyes. Now there's "pure" INTPs and "mudblood" INTPs ... INTPs who actually aren't INTP because their eyes don't reflect TiNe. So what then? We're at the mercy of the video typing experts?
The oft' stated advice to newcomers is to perform a functional analysis of the self. Identify and understand the 8 cognitive functions and their respective polarities, learn how these correspond to the 16 MBTI types.
Ti-dom, check
Fe-inferior, double check
Ne, wtf is that?
Se, ...uhhhh check
Si, check, definitely!

wait ... contradiction already? OK, so NOT Se.
Te? sorta
Ni ... mayhaps
oh well let me just take the cognitive function test
It says I use Se and Si? hrmmm.
It also says I use Te and Ti.
INFJ? No ... wait, they're too rare. No, probably INFJ. Everybody is INFJ these days...
ISTP then! No ... Si (D'OH) Maybe I don't "get" Si.
How come every Si description available rings home then?
I must be Si-dom?
ISFJ then. ... well, no not really. That's not right... Can't I be TiSi? No? DAMMIT.
INTP then ... wait, no ...