When I look at my car it is blue. But just because other people say it is blue as well how do we know that they are seeing it the same way? What if they aren't even real at all and we're just lead to believe that they exist due to our senses fooling us? People hallucinate when put under intense stress so how do we know that we aren't alone in this world but we build the illusion of others around us to keep us from loneliness?