This article focuses on a crucial topic of epistemology in French philosopher Gaston Bachelard: epistemological obstacle. Through bachelardian psychanalysis of scientific mind and its neuroses the author puts a question, if a term of “the guardian of threshold”, used by phenomenological psychotherapy based by Robert Desoille within a method of daydreaming, is or is not narrative reference to analytical thinking about the meaning of epistemological obstacle, which stops scientific knowledge in its progress. The author develops the issue of Bachelard’s rationalism through his own genuine phenomenology, or anthropology of studying man as a man of “twenty-four hours”, but also through Bachelard’s analyses of epistemological obstacle described in his The Formation of the Scientific Mind (originally from year 1938). Between philosophy of reached erudition (by Bachelard own words, a senile state of science) and philosophy, which permanently visits a school, learns and reorganises its knowledge (youth of science) is a dialectical motion of historical epistemology. The science opened to consciousness of its own errors in ways, by which it reaches its knowledge, is for Bachelard materialized in the imagination of overcoming an obstacle, for example such obstacle, which is described by image of the guardian of threshold.