Sapir had a profound influence on Whorf's thinking. Sapir's earliest writings had espoused views of the relation between thought and language stemming from the Humboldtian tradition he acquired through Franz Boas, which regarded language as the historical embodiment of "volksgeist", or ethnic world view. But Sapir had since become influenced by a current of logical positivism, such as that of Bertrand Russell and the early Ludwig Wittgenstein, particularly through Ogden and Richards' "The Meaning of Meaning", from which he adopted the view that natural language potentially obscures, rather than facilitates, the mind to perceive and describe the world as it really is. In this view, proper perception could only be accomplished through formal logics. During his stay at Yale, Whorf acquired this current of thought partly from Sapir and partly through his own readings of Russell and Ogden and Richards. As Whorf became more influenced by positivist science he also distanced himself from some approaches to language and meaning that he saw as lacking in rigor and insight. One of these was Polish philosopher Alfred Korzybski's General semantics, which was espoused in the US by Stuart Chase. Chase admired Whorf's work and frequently sought out a reluctant Whorf, who considered Chase to be "utterly incompetent by training and background to handle such a subject." Ironically, Chase would later write the foreword for Carroll's collection of Whorf's writings.