This is one of those defenses which can be an incredibly healthy thing when it is either age-appropriate or suitable to adaptive needs that fit the context of our lives. It demonstrates how evolutionarily crucial the ego defenses are for our growth and development, and how it is that - maturity appropriate to our age at the time - they may even manage to save us from trouble in the nick of time. Introjection is especially befitted to such a human need, because it is the essence of hero worship. We need heroes throughout our lives, and those moments of tribulation and despair are the ones in which we most desperately need the “self-heroism” of introjection.
It occurs when we take on some idea or admire a person so deeply that they literally “become a part of us,” where our identity takes on some of their identity. Unlike projection - which puts our selves, our imaginations and memories out onto the identity of other people, creating a mirage, falsifying them - introjection takes their true essence into ourselves. Whether the identity of the other person tends more toward the good or more toward the evil is another matter. What is taken in is real, and gives us real, new identity.
In a traumatic experience, for example, introjection may occur when we take on attributes of other people who seem better able to cope with the situation than we do. Or the ultimate introjection that we have covered and will continue to learn from - that of our same-sex and opposite-sex parent. We are forming a new, synthetic identity when we do so.
In a marriage, we do literally take on some identity from the other person, and mutually form a third, new identity as a couple, for example, so introjection is often not at all unhealthy.
However, again, just like any of the defenses, when it’s too much, too often, there is trouble. We might feel about this person as if we “don’t really know them,” as if they don’t really have an identity of their own. If that were the case, then how would we truly know what goals to jointly pursue together. We would have to dictate to them who they even are. How can they have goals? And how could we possibly align goals with such a person?
What we need to know is that long ago, they introjected” their same-sex parent, to have a starting point on who they are as a person, that they “introjected” their opposite-sex parent, which for better or worse, provides them generally what they want in a mate as far as “higher-brained” features, the “identity of the other” - for example, “daddy was a captain of business, but had a big heart” (then you will be the best candidate if you are too), or “mom was the most talented oil painter, and she saved dozens of stray animals in the neighborhood” (then it’s a plus if you have a soft spot for animals and an artistic flair too.) And finally, we need to know that they have the capacity to “introject” us, too. We will be their mate, and are forming a union.
In light amounts, introjection provides us all kinds of things that will benefit us in a mature way. It is what we do with our most admired heroes, or people we seek to emulate in business or in raising a family, we introject our cultural icons and sometimes, on the occasion there are some of merit, our political leaders, bosses and friends.
We will learn how to stop too much of this and have just enough of it in our lives, when we get to the section on the Immature Ego Defenses.