Answer and explanation;
-Some form of skepticism is essential to the scientific method. Ideally, researchers would form hypothesis based on a-prior theories or previous empirical evidence and use formal methods to test them.
-Skepticism can be defined as the attitude of subjecting claims to increasingly difficult tests before accepting them.
-Scientists are 'pretty confident' that life evolves on Earth according to the forces of natural selection because every single test they have made is consistent with this process. They do not 'know' that this is true but they are extremely confident.
