Its epistemological difficulties, always more or less in evidence, have since that day sufficed to discredit materialism, and to foster the growth of a critical and apologetic form of naturalism known as positivism or agnosticism.
"The Approach to Philosophy"
Ralph Barton Perry
In its critical phase, wherein it makes the general assertion that the natural sciences constitute the only possible knowledge, whatever be the nature of reality itself, it is called positivism, agnosticism, or simply naturalism.
"The Approach to Philosophy"
Ralph Barton Perry
This first takes the form of positivism, or the theory that only such nature as can be directly known can be really known.
"The Approach to Philosophy"
Ralph Barton Perry