To facilitate a greater understanding of this concept, consider the following example: Waking up in the morning, you go down the stairs and walk into the kitchen. You open the fridge and on top of the egg box you find a pen. You obviously do not close the fridge door and conclude that the pen’s existence is necessary. You do not think that the pen in the fridge got there by itself. You question why the pen is on top of the egg box. The reason you ask this question is because the pen’s existence on the egg box is not necessary.
