The linguistic relativity (Whorfian) hypothesis states that language influences thought. In its strongest form, the hypothesis states that language controls both thought and perception. Several experiments have shown that this is false. The weaker form of the hypothesis, which states that language influences thought, has been held to be so vague that it is unprovable. The argument presented herein is that the weaker Whorfian hypothesis can be quantified and thus evaluated. Models of cognition developed after Whorf's day indicate ways in which thought can be influenced by cultural variations in the lexical, syntactical, semantic, and pragmatic aspects of language. Although much research remains to be done, there appears to be a great deal of truth to the linguistic relativity hypothesis. In many ways the language people speak is a guide to the language in which they think.