There is no definition of God. That which is defined, is limited. How can we define and limit God? If we could do this, God would not be God, but, instead, we would be gods or at least something superior to God.
Reading Holy Scripture, we can, without fear of being in error, say that God is the highest, infinite, unlimited, perfect spiritual Being from Whom derived all that has been created and is sustained. John the Evangelist says: "God is Spirit." As Spirit, which God is, He does not require space, but rather He fills space; He is, that is to say, present everywhere. He is beyond time; that is, eternal. He is unaffected by change and therefore is unalterable. The Spirit cannot be confined within earthly limits; it does not age, does not accept changes or alterations. Since God has all of these qualities, He is All-knowing. He comprehends everything. He has unlimited knowledge. He knows and has always before Him the past, the present, and the future. Past, present, and future have a meaning for us; but for God, Who is eternal, they have no meaning or significance. Everything is in the present to Him. God is All-wise. And He acts always correctly and with purpose. He is the All-mighty and the Ruler of everything. He is All-powerful; nothing can resist Him. Before Him, "every knee" is bent. Again, John the Evangelist tells us that God is Love. Since He is complete Love, He is also Most-Holy. He is Perfect Goodness. He is the highest justice. He treats all of His creatures with utmost love, justice, and mercy. God is self-sufficient. He has no need whatsoever of anything outside of Himself. He is truly Blessed. Scripture tells us still again that He is Light, the Light of Truth that enlightens and blesses everything.
In addition to all that we have said to now, we can conclude without any doubt that "every perfect Gift is from above;" every good quality is found in God and is directed by God with perfect selflessness and love, and is directed toward His creatures. All of God's actions are for man's good and the good of His creatures. God's perfection and the fact that the world is such an harmonious whole, lead us to the conclusion that God is One. One directing mind that rules everything. There is no greater blasphemy than for someone to believe that many gods exist, one god for heaven, another god for the earth, another god for the sea, another god for Hades, and so forth. Nothing can stand beside the One God.
Some will ask how can you say that we believe in one God when you speak of Father, Son, and Holy Spirit? And again, what position does the Panagia (The Virgin Mary) have in divinity? Is God the Father? Is God the Son? Is God the Holy Spirit? If so, do we not, perhaps, have three gods? And beyond that--is the Panagia a goddess? At this point we will say very simply that the Father is really God. And the Son is God. and the Holy Spirit is God. There are not, however, three Gods. There is one trinitarian God. In another section, we will explain all of this in detail to the extent that the human mind can comprehend it. I say this because, as we said previously, God is infinite and the human mind does not have the capacity to understand that. When discussing theology, we must also bear in mind these philosophical thoughts. Ideas have three categories: logical--that is, those that are in accord with human logic; irrational--which are contrary to human logic and consequently cannot stand; and supra-logical ideas--that is, those ideas that go beyond logic, that are above logic. Supra-logical ideas cannot be investigated by the human mind.
As for the Panagia, the Mother of Our Lord, we can say that of course she is not a goddess. She is herself human. Worshipping her is not permitted. We can, however, honour her. We can request her to intercede for us because her intercession has a powerful influence upon her Son and her God, and our God, Jesus Christ. But we shall speak about our Panagia in another section.Only True, Trinitarian God, All-holy, All-mighty, All-wise, All-loving, All-knowing, Eternal and Unchangeable, Who are present everywhere, accept our humble praise. Receive our thanksgiving and our gratitude, which arises from our sinful hearts, but with sincerity. Hear our supplication. During the course of this catechism, whose purpose is to know You better and to unite us to Yourself, become Yourself the mouth of the speaker. Open the hearts of men to accept Your Word. Abide with us. Let as many people as possible hear Your Word for them to be fertile soil in which Your Word may bear fruit. Gaze with love and goodness upon how men suffer from sin because they are not near You. Redeem us all. Make all of us Yours.