The verification principle – which states that a statement is meaningful if it can be reduced to items of experience and is logically consistent or necessary – isn’t really talking about truth or meaning. It is never-the-less a useful principle because demarcates between the realms of statements that we can verify, about which we can say they true or false and the realms of statements that we cannot verify.
Essientially it is a dicision procedure for ascertaining the truth value of certain statements but just because a statement doesn’t fall within its remit doesn’t mean that the statement is meaningless. It means we are unable to say whether or not that statement is true. This is because the verification principle is really saying something about our capacity to know things and is not a statement about things independent of us.
The belief that meaningfulness is defined as that which can be dealt with by the verification principle is easily broken by the question: “Is the verification principle meaningful?”. Also because the verification principle takes as given two things – namely experience and logic – it cannot of itself attribute meaning to those things. If our cognition or rather our capacity to discover the truth value of statements is expressed by the verification principle (and I believe it is) then we have to take experience and logic on faith. In fact this isn’t a decision we ever make or can make because we just do despite our philosophizing otherwise.
The problem with this is that we cannot help but make metaphysical statements and ask metaphysical questions. By metaphysical I mean that which is outside the remit of the verification principle. We ask questions like “What causes experience?” This is totally meaningless within a system defined by verificationism but never-the-less it is obviously a valid question that arises naturally upon minimal reflection. The verification principle cannot be used to judge any answer to this question because it uses the content of experience – and only the content of experience (Hume showed quite well that logic is nothing but a kind of heuristic conditioning garnered from our experience) – to verify.
It’s like there is a box and we are in the box. We want to know what is outside of the box but all we have to talk about is what is inside the box. Any statement we make will be a statement about the inside of the box. It may be the case that the outside of the box is like the inside of the box, or that it is analogically similar but we cannot decide which of the many statements is true or false until we step outside of the box which we cannot do!