What do you know? Why do you know it? How can you be sure you know all there is to know about it? Let's tackle that last question first. You can't be sure. There is always the possibility that you could be missing a vital piece of information. In the absence of omniscience, all you can do is work on the information you have available to you, having first been humble enough to check your facts. These circumstances seemingly require you to be decisive. If you're really not sure, be clearly, deliberately... indecisive!