Minecraft Will Not Start

What I expected to happen was..:
I expected for Minecraft to start after loading.

What actually happened was..:
After I had pressed play in the launcher, the Mojang thing popped up. It never properly loaded, it wouldn't respond. And once I had closed the window, the launcher popped up and said GAME CRASH. An unexpected error has occurred and the game has crashed. We're sorry for the inconvenience. I left the Mojang thing open for an hour, and it still would not start.

I have also checked crash logs. There are no crash logs. The game will not start.

Steps to Reproduce..:
Open the launcher, and press play.