What is the difference between opinion and knowledge? Everyone has an opinion about something. But what is that opinion based on? Perhaps we don't really know anything, but rather, we only think we know things, and based on that, we are left with empty opinions. How do you know that you know anything? The ancient Greek philosopher Plato had an opinion on how we can attain true knowledge, and in this message, Dr. Sproul helps us understand Plato's thoughts on knowledge.