What is Systems Theory?

I gotta tell ya, writing about theory makes my brain go fuzzy. It must be a side effect of grad school. I am so appreciative of the researchers that tease out behavior and collect it into neat little packages like systems theory, but I hate writing about it. Still, of course, theory is very important to what therapists do. Without it, we would be floundering around, making baseless assumptions and boldly ruining lives, so I owe it to the researchers. If I’m not going to contribute to their work I might as well help others understand it.

On my homepage and sprinkled throughout the blog is the notion that marriage and family therapists can treat individuals as well as couples and families, using something called systems theory. What is systems theory, and how does it help different groups (or non-groups) in the therapy room?

Related: What is Narrative Therapy?


Systems Theory Background

There are a couple things you need to understand in order to really get why this theory works so well. First is the overarching idea, that “the whole is greater than the sum of its parts.” Then comes all the other places we see systems theory working outside the therapy room. This is not just something psychologists made up; it’s everywhere!

The whole systems is greater than the sum of its parts

Everything is made up of parts. We know this from science. Human bodies are made up of organs. Organs are made up of tissue, tissue is made up of cells, cells are made up of atoms. Even atoms have been split to find more parts! That is really, really cool. But the whole system? The thing that all those parts create together? That’s even cooler. 

This is true not only of the human body, but of most things. For our purposes in this section, we’ll focus on people. An individual can be a whole (in the physical sense and psychologically as we’ll discuss below), and so can a couple, a family, a community, a country, and a society. These systems are made up of smaller parts that are great on their own, but when they come together, they can do even greater things. In fact, we team up with people for this exact purpose– to do things we could not do alone.

A couple (historically) could not have a baby without teaming up together. A family could not sustain a household without the others. A community or society could not run smoothly without all the people working together toward common goals. That common goal is homeostasis.


You may remember the term homeostasis from biology. Basically, it means balance. A baseline. That’s exactly what it means in systems theory as well. Essentially, every family, couple, or other system wants to just continue operating at a baseline level. But life is full of constant change and growth. When a change comes at the system, they have to have a plan to get back to baseline, or homeostasis.

When systems have trouble returning to baseline, that’s when they break up, become distant, or cut off from each other. That’s also when they could come to therapy for help managing difficult changes.

Systems did not originate in psychology

Systems theory is actually from lots of other places. In biology, systems theory is used to help describe the way animals work together to form their larger ecosystems. Systems theory in technology describes how different parts of the machine work together to create a functioning program, computer, or what have you. In each of these different forms, you can see how the whole is greater than the sum of its parts.


Systems Theory in the Therapy Room

Couples and Families

Systems theory most obviously applies to couples and families, because they’re the most obvious systems. As stated earlier, we team up with other people to do things we couldn’t do on our own. But sometimes, things don’t work out because the parts aren’t operating in a healthy way. For example, if one person in a system becomes afflicted with trauma, they’re going to interact differently with the other parts, and things will be thrown off balance. If someone in a system loses a job, that affects how the rest of the system can run.



It’s less obvious how an individual can be a system, but it’s true! An individual is a system in many ways. Clearly, they’re systems in a physical sense because of organs and muscle and tissue. But there’s a branch of psychology theory called Internal Family Systems theory, which states that our minds are made up of three types metaphorical parts. Exiles, managers, and firefighters. And then there’s the self.

Exiles are the parts of us that carry our trauma. If they were in charge, we would just always be miserable victims, laying in bed unable to go on with life. Luckily, we have Managers, in charge of keeping them exiled so we can carry out our day-to-day functioning. If they get too much power, we become perfectionists, too rigid and too anxious. If Managers fail, Firefighters take over and quickly clear up emergency situations. Unfortunately, Firefighters often (not always, but often) use dangerous methods like binge drinking, calling your exes, or self-harm.

At homeostasis, the Self leads all of these parts. We need them all, even though they sometimes behave badly. The Self stays in the lead because it is the home of our compassion, leadership skills, and all our other good stuff.

Each of these parts has good stuff, that’s undeniable. That’s why they exist. And yet, on their own, none of them would form a human being that could function well in society. The whole that they all create is greater than the sum of each part.


So that’s basically systems theory! Do you have questions? What are your thoughts? Leave them in a comment below!

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