I strive to live my life according to that caution, and even train others to use this strategy with me to benefit our mutual relationship. I am protective of my "moan space." 

Because people struggle so much with relationships ("can't live with 'em; can't live without 'em"), it's common for new type users to inquire about what types they should foster relationships with, and which types to avoid. (I did!) 

Here's a catalog of every type relationship formula I have encountered. (I've been collecting them for a decade, so I believe my list is comprehensive.) 

First, let's look at friendships. Friendships tend to be qualitatively different from romantic relationships and less emotionally charged, so we'll explore them first. 

Most friendships are based on "common ground." Sometimes that means there's instant affinity and friendship between people with identical type patterns, such as INFJ + INFJ. But it's not a rule! I've also seen two INFJs dislike one another on sight, or react to another INFJ with vicious criticism, or engage in flame wars on internet type lists. 

It's possible Perceiving types are less inclined to "butt heads" with representatives of their identical type pattern, but there’s still no guarantee. I’ve similarly seen a number of perceiving types display animosity and turn on “their own kind.” Simply matching type patterns does not reliably predict a friendship made in heaven. 

This notion of "common ground," however, is a fairly consistent and reliable formula. So the obvious question then is, "What qualifies as 'common ground'?" And the definitive answer is, of course, "it depends." Certainly the answer changes depending on which type model you look to! 

Having a Temperament pattern in common between two people often creates instant rapport. After all, their core Temperament needs match; their Temperament values match; their talents and behaviors match – so rapport is likely to breed easily. Thus, Catalysts are likely to gravitate toward other Catalysts, Theorists toward other Theorists, etc. 

Having similar or complementary Interaction Styles may also produce relationships with magical common ground. In the past month, I’ve heard two ENFJs report thriving relationships with ESTJs, probably due to their having similar Interaction Style energies. (They may make wrong-headed decisions sometimes, but at least they make them quickly together!) The Interaction Style model is an "energetic" model – it’s about the way we express our joi de vivre. So enthusiastic people are drawn to other enthusiastic people; reserved people are drawn to other reserved people, etc. Sometimes we see enthusiastic people try to jolly up reserved folks; and reserved people try to settle down enthusiastic people – but overall it’s easy to see how matching innate energy levels creates a sense of instant compatibility. 

Let's now turn to the familiar psychological type model, first identified by Carl Jung and later popularized by Isabel Briggs-Myers' venerable MBTI. This model has been traditionally taught as a model of four basic functions: Thinking, Feeling, Sensing, iNtuiting. Naturally, each of these processes holds the possibility of being "common ground." Because this model is relatively unsophisticated at this generalized level, it's nearly impossible to suggest any bulletproof algorithms or draw too many precise conclusions about precisely what attracts people to one another. It seems like anything goes! 

There is a more complex version of this model now, based on the pioneering work of Dr. John Beebe, that adds some refinements germane to this exploration of relationships. This more sophisticated version of Jung's model presents us with eight "components" to explore common ground with. So an INFJ and an ISFJ [say] might experience affinity around sharing the extraverted Feeling ßà introverted Thinking dimension. Or an INTJ and an ENFP might experience affinity around sharing the extraverted Thinking ßà introverted Feeling dimension. Or how about ENTJ and ISTP around extraverted Sensing ßà introverted iNtuiting? It becomes easier to notice which functions attract and which ones repel using this eight-function lens. 

Overall, it seems reasonable to conclude that nearly any common ground may serve as a basis for friendship, and there seems to be a lot of "common ground" featured in the psychological preferences model. There are many innate predispositions that may attract others. And that has been pretty well borne out by my own real-life experience. 

So let us now turn to the topic of romance, of soulmates -- the sine qua non of many a Catalyst’s existence. 

It's amusing to note that many people discover the type model and leap instantly to the conclusion that finding a mate with an identical code guarantees a match made in heaven! However, while it is true that many type-alike couples thrive blissfully together, it appears they are generally the exception rather than the rule. 

There was a short-lived dating service that began matching up couples according to similarities, all the way down to precisely matching their type codes. And it fizzled. In the flesh, each of the pairings they suggested liked each other well enough and seemed to get on tolerably, but there was no attraction, no heat, no fire, no passion. By the time the dating service figured out its mistake and began MISmatching couples, it was too late. They closed their doors and went out of business. 

The moral is surely obvious: setting your cap for a mate with an identical type pattern will not necessarily kindle romantic interest, much less ensure success or happiness. As a gambler would lament, "it’s not a sure bet." 

Probably the most infamous type combinations for romantic involvement are those decreed by David Keirsey in Please Understand Me. In this book, Keirsey takes the resolute stance that "opposites attract." The algorithm he outlines for each type in painstaking detail simply consists of mismatching every letter of a pair’s type code so these couples have no alphabet in common. 

His prescription has subsequently met with every possible reaction -- ranging from shock and horror to raging success. 

What few people know is that Keirsey changed his formula in a lesser-known sequel, Portraits of Temperament. In this treatment, Keirsey presents a different ideal. In the updated algorithm, he dismisses the first letter of the code as unimportant, matches the second letter, and MISmatches the third and fourth letters. This brand-new formula pairs NFJs with NTPs and STJs with SFPs, and so on. 

With this new sequence, Keirsey seemed to highlight the importance of matching couples on their Perceiving preferences, perhaps so they would "see" things in the same way. (It also reflected his own choice of marriage partner more accurately.) But it mismatches them in some areas, so there is enough difference to create attraction and interest. 

Before he died, Terence Duniho (of DDLI fame) corresponded privately with me to share his own algorithm (nearly identical to Keirsey's). His formula was to match the first two letters of the type code and MISmatch the last two letters. Terence believed this was the ideal combination, and his own choice of spouse reflected this conviction. This particular combination matches couples together around an overall preference for introversion or extraversion, and (just like Keirsey), seems to allow couples to "perceive" in like fashion. 

If you’re keeping score, that's now two type experts recommending this same essential formula as the prescription for relationship success. 

Dr. John Beebe, curiously enough, happens to agree with Keirsey's original formula in his own investigation of relationships. He reprises Keirsey's first algorithm of having no letters in common. However, Beebe’s reasoning is vastly different! Far from setting up type "opposites" (more about that later), Beebe labels this particular kind of matching opposed codes "inverse relationships." Let me provide a sample diagram. 

ESTP --- INFJ

If I compare these two type codes of ESTP and INFJ, it seems apparent to anyone that these are "opposites" simply because they have no letters in common. It seems like a safe assumption. However, if I extend the diagram so it reflects the entire pattern of all eight cognitive processes, what do you notice?

Beebe classifies this mismatched pairing as an "inverse relationship" because the order of preferences are the same albeit inverted with one another. The favorite process of the ESTP is the inferior process of the INFJ, and vice-versa. The order of processes "mirror" one another, both on the top and on the bottom. 

Using Jungian terms, Beebe states that in this combination, each partner will "cradle" the other's anima/animus "gently." (Ooh, that phrase makes me swoon!) In other words, due to the strengths and weaknesses inherent in this particular combination, each partner will have buckets of patience with their mate's inferior process, or "inferiority complex." (This sounds like a lovely and highly desirable quality to have!) 

Complexifying matters significantly, Beebe concurrently introduces a competing algorithm. He states that "seduction" most often occurs when a person meets their favorite process as the 5th process in another person. He indicates there is an overwhelming attraction between two processes in this combination: 1 + 5. 

Let me clarify with an example. An INFJ’s overall favorite cognitive process is introverted iNtuiting. Their 5th process is its diametric opposite: extraverted iNtuiting. (It's the same process in a different attitude – meaning, the opposition manifests from whether a particular process is used in the inner or the outer world. A difference of direction here typically generates conflict, since what one person shares with the world is what the other person believes should be kept to oneself.) 

According to Beebe, when dominant introverted iNtuiting encounters dominant extraverted iNtuiting, it’s as if they magically combine to form a “giant iNtuition” together. (Surely this characterizes an instance where opposites overwhelmingly attract!) Beebe suggests this compelling attraction is far more common than the inverse relationship he previously described, and claims that the sensation can be highly seductive. (I know what he means; I was in an intoxicating relationship of that sort for several years.) 

There are also archetypal attractions that Dr. Beebe has identified which create various forms of relationship, up to and including codependence! According to Beebe, we all use our auxiliary function to support others and help other people rather than using it on or with ourselves. Thus it is possible to stumble into situations where we feel "needed" because it gives us an opportunity to express our auxiliary process. As Dr. Beebe has said, he tends to "think" for other people; I know that I often "feel" for other people; one of my ENFJ clients tends to iNtuit for other people; and I’ve noticed that my ISTJ sister tends to do Sensing for her family, as does my ISFP friend! It’s easy to see where we can get codependent with others when we feel we are contributing something so fundamentally necessary. It's an easy place to get "hooked" and validated, even when the rest of the relationship is unfulfilling. 

Ta daaaa! Those are all the formulas and combinations I encountered during my research into relationships of attraction based on various type algorithms. 

Now let's explore its corollary: the type "opposite." Here we switch from attraction to repulsion as we delve into what constitutes "type incompatibility." 

Once again, this notion of "type opposites" appears in each of the models. 

David Keirsey caused mass confusion within the Temperament model about what constitutes a "type opposite." In one analysis, he implies that Catalysts and Improvisers are "opposites"; in another treatment he declares Catalysts and Theorists to be opposites. Which are we to believe?! 

In the Interaction Styles model, whatever style is listed on the grid diagonal from our preferred style in the matrix causes us the greatest social styles stress. It might therefore be considered our "opposite." Thus, Chart-the-Course and Get-Things-Going would be opposites; and In-Charge and Behind-the-Scenes would be considered "opposites." And it’s true: I’ve seen (and experienced!) great stress from these dissimilar styles. 

People who prefer Jung's original type model (as represented by 4 functions rather than 8) still interpret entirely mismatched codes as "opposites." Using that framework, INFJ and ESTP would once again be opposed in every way. 

This stance apparently overlooks (Jung's contemporary) Marie Louise von Franz's assertion of Jung claiming that the hardest thing to understand is the same function type with the other attitude. 

Bob McAlpine of Type Resources specifies two kinds of "opposites" derived from Dr. Beebe's 8-function model. The first opposite has been named "Opposing Personality." In this version of "opposites," an INFJ's "opposing type" would be the ENFP pattern. Betwixt these two particular patterns, all eight of the processes are entirely mis-matched, albeit not in precisely opposite order. They might be diagrammed thus:

Surmising that mis-matches such as this in the 8-level model would generate tension was verified recently through research done by Ken Liberty. He took an intimate look at what he calls "attitude-antagonistic couples." This description fits couples who have matching letters in their codes, but their favorite processes are in opposing attitudes, as displayed above. These particular combinations report more challenges within their marriages than couples who are not attitude-antagonistic. John Beebe characterized an attitude-antagonistic relationship he was in once by saying, "there was a fight every other minute." 

I don't mean to imply this sort of relationship will never work – I'm merely reporting how certain combinations appear to be fraught with greater challenges than less-opposed combinations do. 

The second "opposite" Bob details is called a "Dynamic Opposite." With this pairing, an INFJ's dynamic opposite would be the ISTJ type pattern. Betwixt these two patterns, all eight of the processes are also entirely mis-matched, albeit not in precisely opposite order. They are diagrammed thus:

INFJ =	ISTJ =
Ni	Si
Fe	Te
Ti	Fi
Se	Ne
down into the Shadow processes
Ne	Se
Fi	Ti
Te	Fe
Si	Ni

What's different about this pattern is how the INFJ's favorite process is the ISTJ’s 8th, or least-favored process, and vice-versa. These types seem uniquely configured to bring out the worst in each other. (Just my rotten luck; that's the formula of the relationship I have with my sister.) 

One model not detailed at length in this examination is Beebe's Archetypes model. That's because it introduces too many variables to summarize succinctly here. Using this model, we would explore Shadow and all our complexes and the impacts they have upon relationship. From the perspective of this model, it seems only one conclusion may be deftly drawn, which is that:

Each individual loves in the other sex what he lacks in himself.
-G. Stanley Hall

Through the lens of the Archetypes model, we might explore the burning philosophical question: what is the purpose of relationship? Is it to make us happy? Is it to complete us in some fashion? Is it somehow our destiny, for the sake of some indefinable concept called "true" or "unconditional love"? 

What is the reason so many people (especially Catalysts) long to know which type is "best" for them and chase the perfect type "formula," much as Ponce de Leon sought the Fountain of Youth? Frustratingly, we also have a culture which offers us dysfunctional models of relationship so that people generally evaluate their relationships with an eye toward what they get out of them. 

Relying on Jungian concepts and leaning heavily into the framework of psychological types, it seems the true purpose of relationship is to create mirrors. Our relationships act as mirrors of ourselves. Thus, relationships are one of our most powerful tools for growth. The people we are in relationship with act as mirrors, reflecting back our beliefs; and we are their mirrors, reflecting back their beliefs. We tend to project onto others what we cannot (as yet) accept in ourselves. 

One benefit of being in conscious relationship is helping one another retrieve these lost and rejected parts. Recognizing how one aspect of relationship is to heal wounded parts of ourselves goes a long way toward making that process less confusing, since this is uncomfortable, frustrating work. This is where an understanding of the psychological types model supports us and fortifies us with courage to face the daunting challenges that confront us. One way to become conscious around relationships is by accepting only one purpose for relationships (and for all of life!), and that is to decide and be who you really are. Let relationship be about deciding what part of yourself you want to "show up," not what part of another person you can capture and hold. Relationships provide a "contextual field" in which you choose and declare, express and fulfill, experience and become who you really are. Relationship is not about having another complete you; but to have another with whom you share your completeness. 

Relationships (your relationship to all things, in fact) were designed as the perfect tool for individuation. They represent ongoing opportunities for growth. Any time we believe relationship is about anything other than that, the Universe makes fools of us. 

Of course, the irony is that our ego has no control over what we are attracted to. We’re attracted to what we’re attracted to, and that’s that! 

Put another way, you don’t fall in love with a “type”; you fall in love with a person. There’s no telling why one person will hook up with another, and it’s a fool’s game to control or predict what you or anyone else is drawn to. 

The culmination of all my research seems to indicate that type is not a divining rod; it cannot help you accurately identify an ideal romantic partner for yourself. But when a relationship materializes through whatever magical mystical means it may, type is an invaluable tool for understanding oneself, working on oneself, and consciously grappling with one’s own Shadow and personal development. 

Once you become involved in relationship, type provides an excellent system for support, understanding, and forgiveness with each other. It goes a long way toward showing where conflicts and blind spots occur in relationship, and points unerringly to where our developmental issues lie. 

And this, too, has been borne out by my real life experience.

The meeting of two personalities is like the contact of two chemical substances: if there is any reaction, both are transformed.
 -C.G. Jung