Another key elements to Durkheim's theory of knowledge outlined in "Elementary Forms" is the concept of ("collective representations"). ' are the symbols and images that come to represent the ideas, beliefs, and values elaborated by a collectivity and are not reducible to individual constituents. They can include words, slogans, ideas, or any number of material items that can serve as a symbol, such as a cross, a rock, a temple, a feather etc. As Durkheim elaborates, ' are created through intense social interaction and are products of collective activity. As such, these representations have the particular, and somewhat contradictory, aspect that they exist externally to the individual—since they are created and controlled not by the individual but by society as a whole—yet, simultaneously within each individual of the society, by virtue of that individual's participation within society.