When dealing with prophesy, it can be helpful to go back to the deliverance of the Ten Commandments. God spoke directly to Moses and to His people, giving His laws which they must keep. However, the people were frightened by the mere sound of the voice of God, as well as the combined accompanying effects like the thunder and lightning. This gives a valid reason for God to speak through prophets. He attempted to speak directly to the people, but most were unable to handle the raw power of God directly. Thus, God used Moses. Furthermore, using the Ten commandments as a basis, one can begin to understand the reasoning behind prophesy, as many biblical accounts are a direct result of the breaking of these Commandments. God intends to keep us as close to Him as possible, and if they are incapable of handling Him directly, He must use prophets to get His message across.