So why do we need prophets? Well because they speak for God and let the world know what God wants us to do. Here is Dieter F. Uchtdorf of the Fist Presidency and he does an excellent job of explaining why we need prophets. Please take the time to read.http://www.lds.org/liahona/2012/03/why-do-we-need-prophets?lang=eng
I know that there is a modern day prophet here on the earth. He gets direction from God and he does let us know God's will for us.
