In my private practice in Washington, DC, I often have couples who conflate and confuse these two very important concepts. However, it is important to understand the distinction and why one almost always works and the other almost never does.
An ultimatum in the relational context is a demand one partner makes to another for the person to do something or not do something with a threatened or implied consequence.
When we make demands of our partners, they almost always fail. A demand is an attempt to control someone else’s behavior. It is externally motivated because you are asking the person to “do something” or “not do something”. One that I often hear in couples therapy is the threat of ending the relationship if there is infidelity. If you tell your partner that if they cheat on you, the relationship is over. You are using the threat of breaking up to control them. This is where I see people (women and men) get caught up in checking up on their partners, trying to keep tabs on what they are doing and with whom. If this is you, you are attempting to externally control what the other person does. The threat of breaking up hangs over their head, and you hope that this ultimatum is serious enough to keep them from cheating.
However, the problem with ultimatums is that when you attempt to control another person’s behavior with your threat, you create two unhealthy situations. The first is that most people hate the feeling of being controlled. Sometimes, people act out just to prove that they can’t be controlled. Childish and immature? Sure, I see it often. This kind of behavior robs people of the agency of making that choice for themselves. Also, the threat of ending the relationship is risky. In the beginning, when the relationship is good, it might work. However, over time, especially if the relationship hits some bumpy parts (as most relationships do) that threat doesn’t have the same power it once did. Cowardly people may cheat just so you leave them. In that way, they get to be the victim and you the bad person for breaking up because you are “jealous and controlling.” The other risk is that you might get so used to being with someone that even an unsatisfying relationship is better than being alone. If that happens, the partner cheats, and you do…nothing. Get mad, argue, fight, but stay right there. Your ultimatums of breaking up are not taken seriously and treated as a joke. You have now taught your partner that they can hurt you without consequences. This is how people wind up in toxic on again off again relationships. One person gets hurt, they break up, then sometime later, they get back together (without really addressing the underlying problem), rinse and repeat.
A boundary is different. When you set a boundary, you are not attempting to control someone else’s behavior. You are attempting to control your own. You state your intentions for what you want in a relationship. You might say that you will not stay in a relationship with a dishonest person. You’re not telling them what they must do. You are telling them what you will and will not tolerate. They get to choose to respect your boundary or not. Now, people may lie and say they will respect it, then don’t think that what you don’t know won’t hurt you. However, sooner or later, everything done in darkness comes to the light. You don’t have to chase it down. Time really does reveal everything if you are paying attention. When their lies are exposed, this is where you control you – not them. For your boundary to be real – it must have “teeth”. If you said, you would not tolerate this kind of behavior…then don’t! See it for what it is, a disappointment, and move on. When you set healthy boundaries and respect them yourself – the first time – you wind up in healthier relationships. You don’t wind up wanting, hoping, praying that your partner will change and give you what you want or need. You don’t spend days, weeks, months, or years crying in the darkness and wondering why this keeps happening to you. You respect that they made a willful choice not to honor your boundary. They are not your person. Your person will respect you and what is important to you. What I know for sure is that without some severe consequences for the person who broke the trust, the scenario will repeat.
People are afraid to set healthy boundaries because they mistakenly believe that it will mean you will be alone. If you believe this to be true, then it will be. However, I have seen enough healthy relationships to know they are just as real. So, stop giving people ultimatums. Learn to set healthy boundaries and give yourself the gift of self-respect. When you can set healthy boundaries, and follow them with real consequences, you have the best chance of being in a healthy and satisfying relationship.