The article is devoted to a specific ‘riddle’ - the authorship of the work published in 1587 in Madrid: “New Philosophy of Human Nature. Neither Known to nor Attained by the Great Ancient Philosophers, Which Will Improve Human Life and Health”. The author of the work - Oliva Sabuco - under this name it became known, and has been repeatedly reprinted. The innovative idea of the work consisted in the statement that a person, having understood his nature, will be able to find out the natural reasons why he lives and dies, or is ill and will be able to avoid an early or painful death and live happily until he reaches a natural, pain-free death from old age. Sabuko’s proposed physiological justification of the dependence of human health on feelings, emotions and passions correlates with the methodological direction of modern medicine focused on psychosomatics. In 1903 archival documents were found and made public, according to which the author is not Oliva Sabuco, but her father, Miguel Sabuco. For more than a hundred years the dispute about the authorship of this work has been going on. The semantic and content analysis of the text and its correlation with the reconstructed cultural and temporal reality allows us to solve the question in a new way not only about its creator, but also provides material for generalizations of a philosophical nature. The return to the historical-philosophical and historical-scientific circulation of the ideas and discoveries of many forgotten thinkers will help in debunking some ‘obvious’, familiar truths and facts that have turned into prejudices of scientific and mass consciousness.