Möbius Strip

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A Möbius strip made with a piece of paper and tape. If an ant were to crawl along the length of this strip, it would return to its starting point having traversed the entire length of the strip (on both sides of the original paper) without ever crossing an edge. Source: Wiki Commons

The Möbius strip is a construction in which inner and outer are indistinguishable and create the holistic figure of the lemniscate traced back to Greek philosophy.

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The lemniscate of Bernoulli and its two foci.  Source: Wiki Commons

Philosphers as diverse as Bracha Etinger and Slovaj Zizeck are referring to the Mobius Strip as a contruction of integration and wholeness.