ei - GNU Aris Manual
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#### 6.3.4 Existential Instantiation.

- 3x(P(x))
- ———–
- P(a) ; a must not have been used before

Existential Instantiation claims that if there exists an object for which property ‘`P`’ is true, then it can be claimed that some unused object has this property. In this case, ‘`a`’ becomes a placeholder for the object. Variables

Existential Instantiation uses exactly one reference.