What does you know no way of judging the future but by the past mean?

Patrick Henry actually originally came up with this idea. "I know of no way of judging the future but by the past" ~ Patrick Henry. He's saying that history repeats itself. And if we study the past, we could learn from our mistakes and do better with maybe our government, economics...ect in the future and predict whats to come in the future. There are several situations or happenings that go on today that have happened in the past. such as the great depression of 1935, at 2012 the economy is starting to really go down and we might have another depression. There are many many more examples but i cant think of any off the top of my head for i haven't even been around very long to experience very much repetition.