ABSTRACT
In the preceding Chapter we dealt with the truth of beliefs and sentences in cases where this depends only upon observation and not upon inference from previous knowledge. In this Chapter we have to begin the inquiry into sentences of kinds that can be proved or disproved when suitable data derived from observation are known. Where such sentences are concerned, we no longer have to consider the relation of beliefs or sentences to something which is in general neither a belief nor a sentence; we have instead to consider only syntactical relations between sentences, in virtue of which the indubitable or probable truth or falsehood of a certain sentence follows from the truth or falsehood of certain others.
