The Son is the image of the Father

For the Son is the natural image of the Father, unchangeable, in everything like to the Father, except that He is begotten, and that He is not the Father. The Father begets, being unbegotten. The Son is begotten, and is not the Father, and the Holy Spirit is the image of the Son. For no one can say the Lord Jesus, except in the Holy Spirit. (I Cor. 12.3) Through the Holy Spirit we know Christ, the Son of God and God, and in the Son we look upon the Father. For in things that are conceived by nature,* language is the interpreter, and spirit is the interpreter of language. The Holy Spirit is the perfect and unchangeable image of the Son, differing only in His procession. The Son is begotten, but does not proceed.

St. John Damascene
Apology Against Those Who Decry Holy Images
Part III, 3rd Point

Doctrines are not always evident in the scriptures

Where do you find in the Old Testament or in the Gospel the Trinity, or consubstantiality, or one Godhead, or three persons, or the one substance of Christ, or His two natures, expressed in so many words? Still, as they are contained in what Scripture does say, and defined by the holy fathers, we receive them and anathematise those who do not.

St. John Damascene
Apology Against Those Who Decry Holy Images
Part III

Venerating the cross is the same as venerating an image

If I worship the image of the Cross, made of whatever wood it may be, shall I not worship the image which shows me the Crucified and my salvation through the Cross? Oh, inhumanity of man! It is evident that I do not worship matter, for supposing the Cross, if it be made of wood, should fall to pieces, I should throw them into the fire, and the same with images.

St. John Damascene
Apology Against Those Who Decry Holy Images
Part II

There are many unwritten traditions that are handed down

The eye-witnesses and ministers of the word handed down the teaching of the Church, not only by writing, but also by unwritten tradition. Whence comes our knowledge of the sacred spot, Mount Calvary, of the holy sepulchre? Has it not been handed down to us from father to son? It is written that our Lord was crucified on Calvary, and buried in the tomb which Joseph hewed out of the rock, but it is unwritten tradition that teaches us we are adoring the right places, and many other things of the same kind. Why do we believe in three baptisms, that is, in three immersions? Why do we adore the Cross? Is it not through tradition? Therefore the holy apostle says: “Brethren, stand fast; and hold the traditions which you have learned, whether by word, or by our epistle.” (II Thess. 2.15) Many things, therefore, being handed down to the Church by unwritten tradition and kept up to the present day, why do you speak slightingly of images?

I am not to be persuaded that the Church is set in order by imperial edicts, but by patristic traditions, written and unwritten. As the written Gospel has been preached in the whole world, so has it been an unwritten tradition in the whole world to represent in image Christ, the incarnate God, and the saints, to adore the Cross, and to pray towards the east.

St. John Damascene
Apology Against Those Who Decry Holy Images
Part II

Solomon’s temple, like the Church, was decorated by images

The temple which Solomon built was consecrated by the blood of animals, and decorated by images of lions, oxen, and the palms and pomegranates. Now, the Church is consecrated by the blood of Christ and of His saints, and it is adorned with the image of Christ and of His saints.

St. John Damascene
Apology Against Those Who Decry Holy Images
Part II

The Saints are deserving of honor

For if the friends of Christ are heirs of God and co-heirs of Christ, and are to be partakers of the divine glory and kingdom, is not even earthly glory due to them? I call you not servants, our Lord says; you are my friends. Shall we, then, withhold from them the honor which the Church gives them?

St. John Damascene
Apology Against Those Who Decry Holy Images
Part II

Iconoclasm requires one to follow the whole law, and therefore fall from grace

If you give up images on account of the law, you should also keep the Sabbath and be circumcised, for these are severely inculcated by it…But you must know that if you observe the law, Christ will profit you nothing.

St. John Damascene
Apology Against Those Who Decry Holy Images
Part II

The Lord worked out our salvation through matter

It is not matter which I adore; it is the Lord of matter, becoming matter for my sake, taking up His abode in matter and working out my salvation through matter. For “the Word was made Flesh, and dwelt amongst us.” (Jn. 1.14) It is evident to all that flesh is matter, and that it is created. I reverence and honour matter, and worship that which has brought about my salvation. I honour it, not as God, but as a channel of divine strength and grace.

St. John Damascene
Apology Against Those Who Decry Holy Images
Part II

Fidelity to Church tradition, even in the slightest thing, is critical

We are obedient to you, O King, in things concerning our daily life, in tributes, taxes, and payments, which are your due; but in ecclesiastical government we have our pastors, preachers of the word, and exponents of ecclesiastical law. We do not change the boundaries marked out by our fathers (Prov. 22.28): we keep the tradition we have received. If we begin to lay down the law to the Church, even in the smallest thing, the whole edifice will fall to the ground in no short time.

St. John Damascene
Apology Against Those Who Decry Holy Images
Part II