lights out

So suddenly Mathias is acting as if he is afraid of the dark. He has always had a night light in his room but it has not been working for a while so we thought he would be fine in the dark. Suddenly Mathias turns two and he is afraid of the dark. We realized this one night when we shut the door after we laid him down and turned off the hall light. He started screaming but we didn't know why. When we turned it back on to go find out what was wrong, he would stop crying. We then flipped the switch a couple of times to test this and sure enough, the instant you turn on the light he is quiet but when you turned it off he would scream. We thought it was pretty funny. Now once we put him down and close the door he will repeatedly yell out "Light! Light!" until we turn the hall light back on.