  The goal of this article is to give an overview of the current limitations
and epistemological barriers in Science and Scientific Philosophy from a very
general point of view. We first list and define the types of knowledge nous,
doxa and episteme, and the Subject-Observer and Object(s) of study, to proceed
showing the different types of barriers that difficult the knowledge of the
physical world: limitations in the language, in the logic of the
Subject-Observer. Later, we discriminate between technological barriers,
(temporary) limits and absolute epistemic barriers. The last type of limits are
presented and discussed in some detail: the quantum of action, Planck's scale
and quantum gravity (showing the importance of the trans-Planckian scale for
structure formation), the cosmological horizon (a limit to the present
observable Universe) and the event horizons (disconnecting the inside of some
spacetimes from the rest of the Universe). We argue that physical problems in
which absolute barriers seem to determine the end of the attainable knowledge,
are in fact amenable to be studied, at least indirectly.
