One of the more practically important distinctions in CNM ethics is the one between privacy and secrecy. Both involve not sharing information. The difference is in what the withholding is for, and who it protects.

Privacy protects the person whose information it is. Secrecy protects the person doing the withholding, usually at the expense of someone else's ability to make informed decisions.

Where the line sits

Privacy in CNM looks like: not sharing a partner's personal details with other partners, maintaining discretion about what happens in one relationship when talking to people in another, not narrating your sexual or romantic life to everyone connected to you in real time. These are forms of respect for people's autonomy over their own information.

Secrecy in CNM looks like: not telling a partner that you have other partners (or hiding the existence or nature of specific ones), concealing information that would affect another person's sexual health decisions, constructing a version of your relationship situation that prevents a new person from giving informed consent to what they're entering.

The clearest principle: you don't have the right to keep secrets about yourself that prevent other people from making informed choices about their own lives. Your partners don't need to know everything about you, but they need to know enough to make real decisions about whether and how to be in relationship with you.

The common difficult cases

The closeted situation. Not everyone is out about their CNM to everyone in their life. Partners who aren't out to family, employers, or social circles may need to manage information carefully in those contexts. The question is whether their discretion there requires deception of their partners, and it usually doesn't. Partners don't need to be kept in the dark about the existence of other partners just because those partners aren't out to everyone.

Partner confidentiality. When one partner shares something personal, that information isn't freely available to share with other partners, even if the content seems relevant or interesting. "What happens in this relationship stays in this relationship", with the exception of things that directly affect other partners, like health information or relevant relationship changes, is a reasonable default. The difficulty: establishing what constitutes "directly affecting" rather than "interesting" is subjective, and the line is worth discussing explicitly rather than assuming.

The new connection that you haven't mentioned yet. Is there an obligation to inform existing partners immediately when a new connection is developing? CNM structures vary on this, and the answer depends on what agreements are in place. What's not a defensible position: actively concealing a developing relationship from partners who have an expectation of knowing.

Sexual health. Privacy has limits when it touches other people's bodies. A partner's sexual health history and current practices are information they're entitled to share selectively in most contexts, but not from you if you're in a relationship with them and the information affects your sexual health decisions. Treating sexual health information as private-to-yourself-even-from-sexual-partners is secrecy in the harmful sense.

Don't ask, don't tell as a special case

Some CNM structures involve explicit agreements not to share information about outside relationships, "don't ask, don't tell" (DADT). Partners agree that each person can have outside connections as long as neither reports back on them.

This is a real arrangement that some people genuinely prefer. It works when both people have authentically consented to it and find it functional. It becomes a problem when it's used as a cover for one person not wanting to deal with their partner's reality, essentially, preferring not to be confronted with information they've decided to pretend doesn't exist. The difference is usually apparent from whether the DADT agreement was genuinely bilateral or essentially one-sided.

DADT also has limits: it typically can't extend to sexual health information that affects the other person, and it can't be used to justify concealing developments that would change the other person's assessment of the arrangement itself.

Asymmetric information in polycules

In complex relational networks, information travels unevenly. One partner may know something about another partner's relationships that a third partner doesn't. This creates situations where someone is effectively operating on incomplete information about the network they're part of.

The general principle: metamours' personal information isn't yours to share. But the existence of people and the basic shape of relationship networks is usually information that everyone in the network is entitled to. Someone who is connected to you sexually is generally entitled to know who else you're connected to sexually, not the details of those relationships, but their existence.

Managing this carefully, respecting partners' privacy while ensuring that no one in the network is making decisions based on a materially incomplete picture, is one of the genuinely complex ongoing tasks of CNM. There's no simple rule that resolves all cases. The honest effort is what's required.