Rudolph Carnap is not a thinker I have really encountered in the past, but he seems to have some really good things to say.
From The Logical Structure of the World and Pseudoproblems in Philosophy:
The new type of philosophy has arisen in close contact with the work of the special sciences, especially mathematics and physics. Consequently they have taken the strict and responsible orientation of the scientific investigator as their guideline for philosophical work, while the attitude of the traditional philosopher is more like that of a poet. This new attitude not only changes the style of thinking but also the type of problem that is posed. The individual no longer undertakes to erect in one bold stroke an entire system of philosophy. Rather, each works at his special place within the one unified science. For the physicist and the historian this orientation is commonplace, but [b]in philosophy we witness the spectacle (which must be depressing to a person of scientific orientation) that one after another and side by side a multiplicity of incompatible philosophical systems is erected. [/b] ... This requirement for justification and conclusive foundation of each thesis will eliminate all speculative and poetic work from philosophy. [b]As soon as we began to take seriously the requirement of scientific strictness, the necessary result was that all of metaphysics was banished from philosophy, since its theses cannot be rationally justified.[/b] It must be possible to give a rational foundation for each scientific thesis, but this does not mean that such a thesis must always be discovered rationally, that is, through an exercise of the understanding alone.
From Philosophy and Logical Syntax:
Metaphysicians cannot avoid making their propositions non-verifiable, because if they made them verifiable, the decision about the truth or falsehood of their doctrines would depend upon experience and therefore belong to the region of empirical science. [b]This consequence they wish to avoid, because they pretend to teach knowledge which is of a higher level than that of empirical science. Thus they are compelled to cut all connection between their propositions and experience; and precisely by this procedure they deprive them of any sense.[/b]
I realize that there has been much debate and criticism of Carnap’s “verifiability”, but that hardly dents what he is saying here. If you want to understand the world you have to root yourself in the real physical stuff, and then look very closely at your language. You can’t just dream up any old crap and nail words together meaninglessly to justify your BS.