In teaching on the Holy Trinity, Saint Basil was a scholar of Alexandrian theology and its main representatives: Origen and Athanasius of Alexandria. The reason St. Basil wrote this teaching is that the Church was waging a war against the heresies of the Pneumatomachoi and Neo-Aryans. Saint Basil wrote the work On the Holy Spirit between 373 and 375 AD It was written to "Your desire for information, my dearest and deeply respected brother Amphilochius, I highly commend, and your industrious energy no less." The author praises his brother's eagerness to find knowledge. When the apostle Paul writes, “There is one God and Father, from whom are all things, and one Lord Jesus Christ, through whom are all things,” he does not mean that a writer is trying to “ introduce the diversity of nature, but exhibit the notion of Father and Son as unmistakable". To substantiate Orthodox triadology, there was an emerging need for St. Basil to develop clear and understandable terminology. The most plausible of the historical-philosophical sources that the saint used in the doctrine of the differentiation between "essence" and "hypostasis" through the so-called generic principle, is the "Introduction" of Porphyry of Tyre, who was a Neoplatonic philosopher, and "Categories ” by Aristotle. In the understanding of “essence” (in contrast to the terms used by Aristotle, while this term was used by Gregory of Nyssa), there is a place for the orthodox Stoic character. St. Basil characterized the essence of God using the ideas of community, identity, unity, and simplicity, yet the essence of God is still not understandable. The prelate states that the “hypostasis” of the Father has a distinctive characteristic – “fatherhood”, the Son – “filiation” and the Holy Spirit – “…… means of paper … of God, not by means of generation, like the Son, but like the breath of His mouth. and On the Holy Spirit by Didymus (Yonkers, NY: St. Vladimir's Seminary Press, 2011). Paul J. Fedwick, "A Chronology of the Life and Works of Basil of Caesarea," in Basil of Caesarea: Christian, Humanist, Ascetic: Sixteenth Centennial Symposium (Toronto: Pontifical Institute of Medieval Studies, 1981), 16-17. NPNF 3.8.1.1.0.1.2.NPNF 3.8.1.1.0.5.7. NPNF, 3.8.1.1.0.6.9.NPNF, 3.8.1.1.0.13.30.Stephen Hildebrand, The Trinitarian Theology of Basil of Caesarea: A Synthesis of Greek Thought and Biblical Faith (Washington, DC: Catholic University of America Press , 2009), 179.NPNF, 3.8.1.1.0.19.