Do any 3D Venn diagrams exist that have no 2D analogues?

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Discussion Overview

The discussion centers on the existence of three-dimensional Venn diagrams that represent set relationships in ways that cannot be captured by two-dimensional Venn diagrams. Participants explore the definitions of relationships between sets and the implications of dimensionality on these representations.

Discussion Character

  • Exploratory, Debate/contested, Conceptual clarification

Main Points Raised

  • Some participants propose that three-dimensional spheres could be used to create Venn diagrams, questioning whether such diagrams could represent relationships that are not possible in two dimensions.
  • Others challenge the definition of a "relationship between sets," asking if unique common elements qualify as a relationship.
  • A participant suggests that there are structures representable in 2D that cannot be accurately depicted in 3D using spheres, providing an example with specific sets.
  • Another participant notes that Venn diagrams do not need to be restricted to circles or spheres, implying that the dimensionality may not inherently limit the representation of relationships.
  • There is uncertainty about whether it is always possible to create a 3D Venn diagram that equates to a 2D one without restrictions on shape.

Areas of Agreement / Disagreement

Participants express differing views on the definitions and implications of dimensionality in Venn diagrams, indicating that multiple competing perspectives remain unresolved.

Contextual Notes

Limitations include varying definitions of relationships between sets and the potential ambiguity in the shapes used for Venn diagrams, which may affect the conclusions drawn about dimensionality.

SamRoss
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TL;DR
Can any relationships between sets be dreamed up in a 3D Venn diagram that could not be done in a 2D Venn diagram?
If we were to use three-dimensional spheres to represent sets, could a 3D Venn diagram be constructed that could not be drawn as a normal 2D Venn diagram without changing the relationships between the sets?
 
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SamRoss said:
Summary:: Can any relationships between sets be dreamed up in a 3D Venn diagram that could not be done in a 2D Venn diagram?

What's your definition for a "relationship between sets"? If two sets have a unique single element in common, is that considered a relationship?
 
SamRoss said:
Summary:: Can any relationships between sets be dreamed up in a 3D Venn diagram that could not be done in a 2D Venn diagram?

If we were to use three-dimensional spheres to represent sets, could a 3D Venn diagram be constructed that could not be drawn as a normal 2D Venn diagram without changing the relationships between the sets?
You should be able to work this out for yourself. I can think of a structure that can be represented in a 2D Venn diagram that cannot be properly represented using 3-spheres: A = {1, 2}, B = {1, 3}, C = {1, 4}.
The three spheres must all intersect because ## 1 \in A \cap B \cap C ## but if this is the case then the volume ## A \cap B \cap C' ## will not be empty.

Edit: why did you decide to restrict your 3D Venn diagram to 3-spheres: 2D Venn diagrams are not restricted to circles - actually shape doesn't really mean anything in the spaces in which we 'draw' Venn diagrams?
 
Venn diagrams only require closed spaces so 2D does not have to be just circles and 3D does not have to be just spheres. Without the circle/sphere restrictions, it might always be possible to do a 3D that equates to a 2D, but I don't know that for sure.
 

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