Barack Obama's aunt once told him, 'If everyone is family, no one is family.' It is blood that makes a tribe, a border that makes a nation.

The same is true of gatherings. The corollary to this saying: If everyone is invited, no one is invited—in the sense of being truly held by the group.

Having a purpose simply means knowing why you’re gathering and doing your participants the honor of being convened for a reason.

And once you have that purpose in mind, you will suddenly find it easier to make all the decisions that a gathering requires.

What’s wrong with someone who’s irrelevant to the purpose? The crux of excluding thoughtfully and intentionally is mustering the courage to shift your perception so that you understand that people who aren’t fulfilling the purpose of your gathering are detracting from it, even if they do nothing to detract from it.

Particularly in smaller gatherings, every single person affects the dynamics of a group. Excluding well and purposefully is reframing who and what you are being generous to—your guests and your purpose.

• Groups of 6: Groups of this rough size are wonderfully conducive to high levels of sharing.
• Groups of 12 to 15: 12 is small enough to build trust and intimacy, and large enough to offer a diversity of opinion and constructive unfamiliarity.
• Groups of 30: It starts to feel like a party, whether or not your gathering is one. Groups of this size are generally too big for a single conversation.
• Groups of 150: It’s the tier at which, “intimacy and trust is still palpable at the level of the whole group; higher up, the group becomes an audience.”