Mostly based on human senses; vision, hearing, feeling, smell or taste.
Sometimes based on a extention of the above, formed by reasoning or logic.
"After the matrix, reality doesn't quite seem so real anymore."
(2)having no excitement in your life unless you choose to slack off and not work,
(3)leaving this planet the same way you entered, naked and cold.
(4)busting your ass to afford your bills while some cocksucker with rich parents gets everything handed to him for free.