There are 3 things that could destroy one of the greatest stock rallies of all time

AP Images / Richard Drew The ongoing equity bull market is the third-longest in history, and it's showing few signs of slowing down. Morgan Stanley thinks the current cycle could end sometime in 2018, and it lays out the three most likely negative catalysts. As the equity bull market stretches well into its ninth year, it looks virtually unstoppable. Formidable earnings growth, easy lending conditions and a gradually expanding economy have combined to cultivate an environment that's been ideal f...