Is this the topic you have been assigned? I wholly disagree with the statement, on principle. If reality were truly in the eyes of individuals, nothing would in fact be real, it would all be individual perception. I think this idea goes along the lines of the current pop-cultural notion that there is no such thing as absolute truth. What a dangerous idea.
If I were writing this essay, I'd talk about the dangers of believing that reality is in the eye of the beholder. Consider what this would mean for law enforcement, consequences of bad decisions, and general societal peace.