Indeed, Kant's strongest argument against the earlier metaphysicians was that they wrongly ascribed existence to alleged beings and realities beyond sense experience.
Russell rejected the unintelligible claims of idealist metaphysicians and, inspired instead by the precision of mathematics, he developed the theory of logical atomism.
The question still remains, though, why a metaphysician would want to adopt a recommendation like this if it rendered meaningless everything the metaphysician said.
Nevertheless, fears of violating the verification principle still lingered in the minds of metaphysicians and moralists, many of whom avoided straying too far from empirical facts.
He argued that the material mode, commonly used in philosophy, frequently leads to the ambiguities and errors of metaphysicians and in generalis the source of meaningless philosophical controversy.
Most of the great ambitious attempts of metaphysicians have proceeded by the attempt to prove that such and such apparent features of the actual world were self-contradictory, and therefore could not be real.
The dogmatic character of metaphysics was made clear particularly by the variety of conclusions to which metaphysicians had come in their systems of thought, as shown by the differences between Descartes, Spinoza, and Leibniz.
From this point of view he thought it foolish for metaphysicians to construct systems of knowledge even before they had determined whether, by pure reason alone, we can apprehend what is not given to us in experience.