The main vehicle to convert your conscious perceptions into the world’s model you have developed is speech, active use of language. Aside from its grammatical structure and lexical material, each verbal statement has (1) an explicit or implied piece of knowledge (“theme” in communicative linguistics) that is set for cognitive transformation and (2) a piece or pieces of knowledge (“rheme”) that are used to configure or reconfigure the theme. Themes are dynamic by the speaker’s intent, they are being actively transformed in his or her statements. Rhemes are static, taken at face value and incorporated as such in this attempt to modify a part, big or small, of the world as you know it.
Take this simple statement: “This flight is being delayed for 3 hours already.” This flight is the knowledge which is being reviewed. The intent of the statement is to modify it. So how do you accomplish this? You apply the static pieces of common knowledge that are not questioned or revisioned in this sentence – “is being”, “delayed”, “for”, “3”, “hours” and “already”. These are rhematic elements; they are grammatically and cognitively arranged to change the notion (idea, perception, concept, etc.) of “this flight”. Consider a response to this statement: “These hours are like days to me.” Now the other person actively modifies the notion of “3 hours” by arranging the rhematic elements of “are”, “like”, “days”, “to” and “me”.
This is a universal linguistic phenomenon. Some languages manage this topic-comment protocol by the word order (English), some by grammatical forms (Japanese), many by intonation – melody and pausation. Very often languages apply more than one rule to define the theme-rheme relationship.
Conscious perceptions is key here. Something that people can formulate verbally gets transformed with this omnipresent and powerful mechanism.