Grice on mode

Grice proposes two types of operators, OpA and OpB. 

The operators grouped together as OpB can be divided into two types: OpB1 and OpB2. A-type operators, on the other hand, represent some degree or measure of acceptability or justification. 

They can take scope over either of the B-type operators, yielding OpA1 + p for an expression of “it is probable that
p” and OpA1 + OpB2+ ! + p” for an expression of “it is desirable that p”. 

Generalising over attitudes he proposes ‘X psi-1 p' for believes and “X psi-2 p” for wants. Psi-3 is concerned with an attitude of deciding whether to believe p or not, while psi-4 with 'want to decide whether to will p or not.'

Grice suggests an operator OpIS corresponding to any particular propositional attitude psi-3, where
‘I’ is a dummy taking the place of either 1,2,3,or 4, and where ‘S’ is a dummy taking the place of either A or B.