Popper on clarity and critical discussion

… [Whenever] we try to propose a solution to a problem, we ought to try as hard as we can to overthrow our solution, rather than defend it. Few of us, unfortunately, practise [sic] this precept; but other people, fortunately, will supply the criticism for us if we fail to supply it ourselves. Yet criticism will be fruitful only if we state our problem as clearly as we can and put our solution in a sufficiently definite form – a form in which it can be critically discussed.

Karl Popper, The Logic of Scientific Discovery (1959)
Preface, p. 16

Popper opens his tome with this description of how a scientific theory should be formulated; it should be clear and it should be open to criticism. Whether it is the Freudian psychoanalyst saying "oral fixation" or the creationist saying, "irreducibly complexity", we can not evaluate scientific ideas without our arsenal of critical analysis. That means not only knowing what X is, but also what X is not.