We intend to show that, on the contrary to what the common sense presumes, it is possible to separate the problem of the science nature from the problem of truth, that is, one can establish criteria according to which a knowledge is legal, although one can never know wether it, or another, is true, and apply the same criteria to identify and disqualify pseudo-knowledge. In order to deal with this question, familiar to the Philosophy of Science, we took as an example a thinker who is a predecessor, the empiricist philosopher of the XVIII century, David Hume.
Demarcation; science; metaphysics; empiricism; cepticism