Page:Schlick - Gesammelte Aufsätze (1926 - 1936), 1938.djvu/385

 was actually a nonsensical combination of words. A genuine question is one for which an answer is logically possible. This is one of the most characteristic results of our empiricism. It means that in principle there are no limits to our knowledge. The boundaries which must be acknowledged are of an empirical nature and, therefore, never ultimate; they can be pushed back further and further; there is no unfathomable mystery in the world.

The dividing line between logical possibility and impossibility of verification is absolutely sharp and distinct; there is no gradual transition between meaning and nonsense. For either you have given the grammatical rules for verification, or you have not; tertium non datur.

Empirical possibility is determined by the laws of nature, but meaning and verifiability are entirely independent of them. Everything that I can describe or define is logically possible — and definitions are in no way bound up with natural laws. The proposition ‘Rivers flow uphill’ is meaningful, but happens to be false because the fact it describes is physically impossible. It will not deprive a proposition of its meaning if the conditions which I stipulate for its verification are incompatible with the laws of nature; I may prescribe conditions, for instance, which could be fulfilled only if the velocity of light were greater than it actually is, or if the Law of Conservation of Energy did not hold, and so forth.

An opponent of our view might find a dangerous paradox or even a contradiction in the preceding explanations, because on the one hand we insisted so strongly on what has been called the “empirical-meaning requirement”, and on the other hand we assert most emphatically that meaning and verifiability do not depend on any empirical conditions whatever, but are determined by purely logical possibilities. The opponent will object: if meaning is a matter of experience, how can it be a matter of definition and logic?

In reality there is no contradiction or difficulty. The word ‘experience’ is ambiguous. Firstly, it may be a name for any so-called ‘immediate data’ — which is a comparatively modern use of the word — and secondly we can use it in the sense in which we speak e.g., of an ‘experienced traveller’, meaning a