Socionics uses a stack of all eight functions, as opposed to the four function stack that is often seen in MBTI. This is called Model A, and it builds up the basics of the theory. This stack can be split up in several ways. First, there are four functions that we “value” and four that we don’t. Model A’s valued functions are the same as MBTI’s valued functions and can be presented in the familiar I/E, S/N, F/T, P/J pattern. (Introverts switch the J and P, since socionics uses this to point at the dominant function rather than the highest extraverted function.) The functions that we don’t value follow the pattern of our type but with the opposite J/P. So an INTP (INTj or LII; you can read why here) has the following stack, with the strongest appearing top to bottom, and the functions on the left being the ones we focus on, or value.
Ti – Ni
Ne – Te
Si – Fi
Fe – Se
So an INTP (Ti-Ne) has as strong Ni as an INTJ, but prefers not to use it. The valued functions are processes that we prefer, that we place value on, while the opposite are functions that we prefer not to use. Neither the functions nor the information coming from them holds much value to us.
The second way they can be divided is through four different “blocks”. The first is the ego block, comprised of the first two valued functions. In the example of an INTP, these functions are Ti and Ne. The ego block is the main program of a person, the operative system of one’s psyche. When faced with a challenge, this is what we prefer to use. It’s our intuitive response to things. It’s “me”. The second block is the id block, the opposite of the ego block. For INTP, this consists of Ni and Te. It’s unvalued and an unconscious process. We’re very comfortable with our skill in these areas, but it’s boring and seen as pointless. We usually see its use as a meaningless activity, unless it’s for a specific purpose. We act by instinct, but are good at retracing our thought process. The third block is our super-ego. For an INTP, this is Fi and Se. It’s a conscious weak spot we have, and we take comments on it as ill-meaning critiques. The fourth block is super-id, consisting of the tertiary and inferior functions. For INTP, these are Si and Fe. This is what we want but can’t provide for ourselves. We know we’re bad at it, but it’s highly valued. Because of this, we want help with it from other people, and compliments on this are highly appreciated and motivating. The super-id block complements one’s ego, and, when strengthened, balances it. It’s the source of many wishes, goals, and cravings.
Another important aspect is the quadras, the most common method of grouping the types (and essential for understanding intertype relationships). A quadra is a grouping of types that share all of the same valued functions — for example: INTP, ENTP, ISFJ, and ESFJ. The quadras share specific values and attitudes towards both the functions and life, and are very useful in explaining types and the roles they play in society. They are usually explained through age. Alphas (SFJ and NTP) start as children, looking at the world in wonder, trying to understand and make sense of it. They are light and merry. Betas (NFJ and STP) represent adolescence, the teenage years. They are darker and heavier, more revolutionary and focused on bringing a new age with them. They are idealistic and good at turning those ideals into reality. Gammas (NTJ and SFP) are adults, business-like and realistic. They are focused on individuality and progress. Deltas (STJ and NFP) represent old age, when things settle down and all is calm. Deltas are focused on the little wonders in life, and are very stable.
So about the names. In MBTI, the P in INTP comes from the fact that INTP’s first extraverted function is a perceptive function, even though its dominant function (Ti) is a judging function. In socionics however, the J or P comes from the dominant function. Therefore, since INTP’s dominant function is a judging function, INTP in socionics becomes INTj (lowercase p or j). More commonly, though, you’ll see INTP called LII. This stems from an entirely different model. In this model, S stands for sensing, I for intuition, L for thinking (logic), and E for feeling (ethics). The first letter corresponds with the dominant function so, for an INTP with dominant thinking, it’s L. The second letter corresponds to the second function — intuition for an INTP, hence I. The last letter is decided by whether the first function has an introverted or extraverted attitude, and is therefore always I or E respectively. INTP’s first function is introverted thinking, so the last letter is an I. This results in the name LII.