1. All great scientific theories mean a new conquest of the unknown. sirkarl raimund popper

If we admit failure too easily, we may not realize that we are very close to being right. -karl popper (m.taiks.com)

3. Science and scientific knowledge are always hypothetical: it is speculative knowledge. The scientific method is the method of criticism: the method of finding and eliminating mistakes and serving the truth. sirkarl raimund popper