In this paper an attempt is made to contribute to a further examination and analysis of the philosophical-theological background of the distinguished intellectual Nicolaos Kerameus, as well as of the development of his thought according to the manuscript ΜΠΤ254 (National Library of Greece) containing an unpublished letter addressed to the Patriarch of Jerusalem Nectarios and attributed to Kerameus. The latter was indeed a scholar endowed with significant skills, a wide erudition among his contemporary savants and an author with a considerable impact on the first half of the 17th century.