What is metaphysics? The question itself is a study in the answer, as to question the meaning of truth is to compare and contrast it to all that we perceive from our senses as 'real.' The principle of verifiability was at the core of Logical Positivism, the movement that sought to apply logic and the methodology of the empirical sciences to all fields of thought. It states that a theory, or more generally a sentence, that is not at least capable of empirical verification is meaningless. For positivists, the 'given,' which can be based primarily upon appearances, is a single, one-dimensional and positive object. There is no elaboration or variation on how the 'given' is interpreted, it simply is. As Schlick tells us (from the positivist outlook), "Only the given is real." This obviously presents contradictions if one is attempting to explain something outside the sphere of what is perceived to be the given. If there is an existence of an external world, then how can the problem be resolved without looking beyond what is known of the given? This is metaphysical idealism, where the philosopher feels he can speak to only that which is given to him -- a kind of solipsistic thought where nothing can be assumed that is not known.
             Schlick attempts to make clear the claims of scientific inquiry in relation to metaphysics -- scientists who state hypotheses without being able to back up their claims with hard facts present a logical impossibility. Facts that cannot be verified -- that is, those that are accepted merely because there is a scientific principle that stands behind them, are logically meaningless. To be logically meaningless, or more simply, 'unthinkable', should have no place in the scientific community, as all scientific thinking should be able to cite not just principles, but the reasons for the effect. Observation, altering the given state -- these things should be taken int...