On the polytheistic gods:

For the truth shall be spoken; since of old these evil demons, effecting apparitions of themselves, both defiled women and corrupted boys, and showed such fearful sights to men, that those who did not use their reason in judging of the actions that were done, were struck with terror; and being carried away by fear, and not knowing that these were demons, they called them gods, and gave to each the name which each of the demons chose for himself (Chapter 5).

On worship of the Trinity:

But both Him, and the Son (who came forth from Him and taught us these things, and the host of the other good angels who follow and are made like to Him), and the prophetic Spirit, we worship and adore, knowing them in reason and truth, and declaring without grudging to every one who wishes to learn, as we have been taught (Chapter 6).

On the judgement and eternal damnation:

[E]ach man goes to everlasting punishment or salvation according to the value of his actions. For if all men knew this, no one would choose wickedness even for a little, knowing that he goes to the everlasting punishment of fire; but would by all means restrain himself, and adorn himself with virtue, that he might obtain the good gifts of God, and escape the punishments (Chapter 12).

Implies that Jesus Christ is not equal to God:

[W]e reasonably worship Him, having learned that He is the Son of the true God Himself, and holding Him in the second place, and the prophetic Spirit in the third, wewill prove. For they proclaim our madness to consist in this, that we give to a crucified man a place second to the unchangeable and eternal God, the Creator of all; for they do not discern the mystery that is herein, to which, as we make it plain to you, we pray you to give heed (Chapter 13).

[W]e assert that the Word of God was born of God in a peculiar manner, different from ordinary generation, let this, as said above, be no extraordinary thing to you, who say that Mercury is the angelic word of God (Chapter 22).

[Comment: This is a strange comparison given that orthodoxy teaches that Jesus Christ is eternally begotten, but Mercury in Roman mythology is not. Even Origen taught that Jesus Christ was eternally generated.]

Celibacy was a common virtue in early Christianity:

[M]any, both men and women, who have been Christ’s disciples from childhood, remain pure at the age of sixty or seventy years; and I boast that I could produce such from every race of men (Chapter 15).

Marriage is for making babies, not for dealing with lust:

But whether we marry, it is only that we may bring up children; or whether we decline marriage, we live continently (Chapter 29).

Christians shall be known by their works:

[L]et those who are not found living as He taught, be understood to be no Christians, even though they profess with the lip the precepts of Christ; for not those who make profession, but those who do the works, shall be saved, according to His word: “Not every one who says to Me, Lord, Lord…”And as to those who are not living pursuant to these His teachings, and are Christians only in name, we demand that all such be punished by you (Chapter 16).

Justin Martyr is aware of traditions we are not privy to:

We find it also predicted that certain persons should be sent by Him into every nation to publish these things, and that rather among the Gentiles [than among the Jews] men should believe in Him. And He was predicted before He appeared, first 5000 years before, and again 3000, then 2000, then 1000, and yet again 800; for in the succession of generations prophets after prophets arose (Chapter 31).

Early Christian repentance:

I will also relate the manner in which we dedicated ourselves to God when we had been made new through Christ; lest, if we omit this, we seem to be unfair in the explanation we are making. As many as are persuaded and believe that what we teach and say is true, and undertake to be able to live accordingly, are instructed to pray and to entreat God with fasting, for the remission of their sins that are past, we praying and fasting with them. Then they are brought by us where there is water, and are regenerated in the same manner in which we were ourselves regenerated. For, in the name of God, the Father and Lord of the universe, and of our Saviour Jesus Christ, and of the Holy Spirit, they then receive the washing with water (Chapter 61).

An interesting explanation of what the term “enlightened”/”illumined” means in Heb 6:4-

And for this [rite] we have learned from the apostles this reason. Since at our birth we were born without our own knowledge or choice, by our parents coming together, and were brought up in bad habits and wicked training; in order that we may not remain the children of necessity and of ignorance, but may become the children of choice and knowledge, and may obtain in the water the remission of sins formerly committed…this washing is called illumination, because they who learn these things are illuminated in their understandings. And in the name of Jesus Christ, who was crucified under Pontius Pilate, and in the name of the Holy Ghost, who through the prophets foretold all things about Jesus, he who is illuminated is washed (Chapter 61).

Baptism by full immersion referenced indirectly:

And the devils, indeed, having heard this washing published by the prophet, instigated those who enter their temples, and are about to approach them with libations and burnt-offerings, also to sprinkle themselves; and they cause them also to wash themselves entirely, as they depart [from the sacrifice], before they enter into the shrines in which their images are set (Chapter 62).

[Justin Martyr makes the case over a couple dozen chapters that Satan copied aspects of the true religion (Christianity) and put it into paganism to deceive many. So, when Justin says that the pagans wash their whole bodies in a Satantic mimicking of baptism, it does reflect what the commonly understood mode of baptism was.]

Justin Martyr presents the Gospel:

He appeared in the shape of fire and in the likeness of an angel to Moses and to the other prophets; but now in the times of your reign, having, as we before said, become Man by a virgin, according to the counsel of the Father, for the salvation of those who believe in Him, He endured both to be set at nought and to suffer, that by dying and rising again He might conquer death (Chapter 63).

Description of early Christian worship. The Elder/Overseer is called a “President:”

[O]n the day called Sunday, all who live in cities or in the country gather together to one place, and the memoirs of the apostles [the Gospels] or the writings of the prophets [Old Testament] are read, as long as time permits; then, when the reader has ceased, the president verbally instructs, and exhorts to the imitation of these good things. Then we all rise together and pray, and, as we before said, when our prayer is ended, bread and wine and water are brought, and the president in like manner offers prayers and thanksgivings, according to his ability, and the people assent, saying Amen; and there is a distribution to each, and a participation of that over which thanks have been given, and to those who are absent a portion is sent by the deacons…Sunday is the day on which we all hold our common assembly, because it is the first day on which God, having wrought a change in the darkness and matter, made the world; and Jesus Christ our Saviour on the same day rose from the dead (Chapter 67).

[Keeping with the First Apology, it appears that Justin Martyr did not have the Epistles in mind when speaking of the Scripture. He does not quote them once in the book. Yet, he quotes the Gospels and the Old Testament extensively.]

Real Presence of Jesus Christ in the elements is affirmed:

For not as common bread and common drink do we receive these; but in like manner as Jesus Christ our Saviour, having been made flesh by the Word of God, had both flesh and blood for our salvation, so likewise have we been taught that the food which is blessed by the prayerof His word, and from which our blood and flesh by transmutation are nourished, is the flesh and blood of that Jesus who was made flesh (Chapter 66).