Circular reasoning occurs when you use A to prove B and B to prove A. For example, we can tell how old the rocks are by the fossils that are in them, and we can tell how old the fossils are by the rocks they are in. All methods of determining the age of fossils use circular reasoning. Initial assumptions are made, and these uncheckable assumptions are what really determines the age of any fossil. In other words, fossils can be made as old or as young as the scientist likes, and there is no way to really know how old the fossil is.

We know how old the rocks are because of the fossils in them. We know how old the fossils are because of the rocks they are in. We know that evolutionists use this circular reasoning because of the rocks in their heads.

Evolution isn't science.