Grice on "φ(θ2/θ1" (in Davidson/Hintikka, p. 125)

The fourth and last glossary point for Grice's natural deduction system involves the use of

"/"

to indicate replacement.


Thus:

where θ₁ and θ₂ are 'terms' (constants of individuals or bound variables),

"φ(θ₂/θ₁"

will read as

"the result of replacing each occurrence of

θ₁ in φ by an occurrence of θ₂, while

preserving subscripts at substitution points." (The upper

symbol indicates the substituend).