Full Idea
The meaning of a sentence is to be defined by reference to the actions to which asserting it would lead.
Gist of Idea
Sentence meaning is given by the actions to which it would lead
Source
Frank P. Ramsey (Facts and Propositions [1927], p.51), quoted by Ian Rumfitt - The Boundary Stones of Thought
Book Reference
Rumfitt,Ian: 'The Boundary Stones of Thought' [OUP 2015], p.102
A Reaction
I find this idea quite bizarre. Most sentences have no connection to any action or behavior at all. Do we have to ingeniously contrive some possible action? That is the worst sort of behaviourism. See context - Ramsey wasn't stupid!