All we know if an angel is that it is incorporeal, immaterial, and only by comparing it with God-who is incomparable-can we see that it has some density and body after all, since in reality only God is truly immaterial and incorporeal.

An angel is an intelligent essence, always in motion. It has free will, is incorporeal, serves God, and has been bestowed with immortality. Only the Creator understands its true nature.

And all that is therein; Invisible and visible, Their notes let all things blend, For Christ the Lord is risen. Our joy that hath no end.

The Eucharist is a fire which inflames us

Both angels and demons are ignorant of the future, yet they make predictions. The angels do so when God reveals the future to them and commands them to prophesy, and what they prophesy comes to pass. Demons also make predictions, but these are only guesses based on what they see from afar.

If a pagan asks you to show him your faith, take him into church and place him before the icons.

Think of the Father as a spring of life begetting the Son like a river and the Holy Ghost like a sea, for the spring and the river and sea are all one nature. Think of the Father as a root, and of the Son as a branch, and the Spirit as a fruit, for the substance in these three is one. The Father is a sun with the Son as rays and the Holy Ghost as heat.