The article contends that Petrić, taking upon himself the problem of One, the focus of his work Nova filozofija o sveopćem (New Philosophy on the Universal), is a link in the endless chain of those who have dealt with this problem before and after him. The sphere of themes is then determined by that tradition within which we attempt to perceive the premises of Petrić's contemplating the one, and to overview the specific nature of his solution. The entire debate on One (Unum-principium) is first connected with contemplative assumptions of the work Nova de universis philosophia (as well as his part Panarchia where he works explicitly on these problems), presented in an earlier work, Discussiones peripateticae. There Petrić, on the basis of a critical analys1is of Aristotle's philosophy and a comparison of this with the Pythagorean-Platonic-Egyptian-Caldean spiritual tradition, outlines the direction in which he will move in order to construct his »new« philosophy, -and which will be both philosophy and sapience (theology), actually a »pia philosophia«. Resolution of the problem of One (Unum-principium) in New Philosophy represents elaboration of the project outlined in Discussiones. The basic theses of the Unum-Principium are subsequently derived on the basis of Petrić's text Panarchia, and then, with a critical distance towards the usual qualification of Petrić's philosophy (as »Neoplatonic«), a more precise determination of the character of his solutions was attempted on the assumption of respecting all segments of the tradition of thinking on the One, which Petrić invoke s expressis verbis. Thus lit can be that present in his approach to the problem of One, and in his final solutions, along with an unquestionable basis in the Neoplatonic phi1osophers, there are also elements of the entire neo-Platonic tradition, including the Caldaean Prophecies and Hermetic Writings. This finally is emphasized in individual segments of his outline but also in the basic line of founding his interpretation of reality. The relevant parts of this interpretation are those where the Unum (principium) is differentiated as the unum absolutum-transcendent, the uncognizable One-and essentialy One (unum essentilale), the differentiated One, the first Oneness (unitas), which contains all onenesses (unitates) - which differentiation on the model of those writings in the middle part of the Panarchia will be exhibited in the sense of a trinum-unum-principium (One-first mind, the second mind and love towards the first One as a return to the source), and related to the Christian teachilings of the Trinity, so that a relation of aspects of the Unum-principium win be established as a relation of divine persons. This will have far reaching effects in terms of the basic line of Petrić's development of the relations of Unum (principium)-omnia (the principium Unomnia), which is particularly predominant in the last book of the Panarchia, in which and again, relying on these writings, he develops theses on God (God and One being the same) which is all (Universum) and in everything, actually that from which all is as that through which everything manifests itself, namely through that it is, and according to the essence (to the mind as the Creator with One co-essential), through that what that is, therefore theses on the super-essential One-eternal possibility that there be a being, with the principle .of production, out-coming in the will to be a being, bonded to the creative mind.