Linguist Benjamin Lee Whorf is born. According to Whorf, language exists in our mind prior to our experience of reality and thus language serves to shape and define our reality.
Because of this, people who share a language also share a binding agreement as to what reality is. On the other hand, people with different languages literally have different realities.
Benjamin Lee Whorf's linguistic relativism was popular in the 1950s but has since been discredited. One of the ideas used to support this principle was the claim that the Inuit (Eskimos) have large numbers of words for the concept of "snow," whereas English has only one. Thus, the reality of the Inuit consists of much more subtlety and variation (at least where snow is concerned) than does the reality of English speakers.
Unfortunately, both premises in the above example are false. The Inuit do not have large numbers of words for the concept of snow, and English has many (flurries, sleet, etc.). Despite this and many other facts (like how color terminology in various languages seem to follow nearly identical structural patterns) which demonstrate that linguistic relativism simply isn't true, it has managed to retain some popularity.
There are still social and psychological theories which simply assume that our language is instrumental in forming our reality.