# EYE socket: where the light bulb meets the electricity

:bulb: __arrows__
- queries use an upwards double arrow `=^`
- backward rules use a leftwards double arrow `<=`
- forward rules use a rightwards double arrow `=>`

:warning: __variables__
- only `_:x` blank nodes in triples and quads
- only `?x` quickvars in rules and queries
- quantified `var:x` variables in proofs

:information_source: __triptych__
```
        eye                     observership
         u                       /        \
        =^                      /          \
   l <= eye => r            origin ------ evolution

Euler lost both eyes        Hawking-Hertog triptych
```
