Ayer's Language Truth & Logic claims that the principle of verification is what makes propositions meaningful. And the principle itself is Experience. But 'Experience' is vague and needs to be defined.
There is a "weak" and a "strong" kind of verification that Ayer gives:
The "weak" kind is where a particular sense-experience confirms a proposition.
For example, let's say that we have the proposition, "My dog barked.", then I could find out if the proposition "My dog barked" (Bd) is true by checking Experience for the sound of 'my barking dog'. This verification is weak because Bd itself is not something you hear, since Bd is a proposition and not a sense experience. Your experience of Bd is not Bd itself.
The "strong" kind of verification is the other type that explains a sense-experience.
So if an observation statement explains the barking dog in a given time and place, then that statement is meaningful because it explains the experience of a barking dog. This verification is 'strong' rather than 'weak' because propositions that can be verified are either statements of Experience or your experience of Experience.
So making Meaning out of a given proposition is a private experience, whereas verification requires both the proposition and the experience of who formed the proposition. So we make Meaning out of propositions that have been confirmed by others, who have had the experience of what those propositions refer to.
