set of hypotheses which may be either true or false and have to be tested by experience. It is not necessary to make hypotheses about meaning, and they would come too late, because we must presuppose meaning in order to formulate any hypothesis. We have not made any assumptions, we have done nothing but formulate the rules which everybody always follows whenever he tries to explain his own meaning and whenever he wants to understand other people's meaning, and which he never actually violates — except when he begins to philosophize.
In establishing the identity of meaning and manner of verification we are not making any wonderful discovery, but are pointing to a mere truism. We are simply maintaining that a proposition has meaning for us only if it makes some kind of difference to us whether it is true or false, and that its meaning lies entirely in this difference. Nobody has ever explained the meaning of sentence in any other way than by explaining what would be different in the world if the proposition were false instead of true (or vice versa).
This, I am sure, cannot be denied. But the great objection usually raised against the view I have been defending consists in maintaining that the "difference in the world" expressed by the proposition may not be observable or in any way discoverable. In other words: if a sentence is to have meaning for us we must, of course, know which fact it expresses, but it may be absolutely impossible for us to find out whether the fact actually exists. In this case the proposition could never be verified, but it would not be meaningless. Therefore, our adversaries conclude, meaning is distinct from verifiability, and not dependent upon it.
This argument is faulty on account of an ambiguity of the word "verifiability". In the first place, one might call a proposition verifiable, if the actual facts are such as to permit our finding out its truth or falsity whenever we feel like it. In this sense it would be impossible for me to verify the statement: "there is gold to be found in the earth 300 feet below my house", for there are many empirical circumstances which absolutely prevent me from discovering its truth; and yet the assertion was certainly not nonsensical. Or take the statement: "On the back side of the moon there are mountains 10.000 feet high". It is not improbable that no human being will ever be able to verify or falsify it, but what philosopher would be bold
