1. II. Light and Darkness (1:5-2:24)
    1. C. Test of Love (2:7-2:17)
      1. ii. Merits of stages of Christian growth (2:12-2:14)

Calvin

2:12
This verse is still a general address, re-iterating the forgiveness of sins. Calvin hangs on a wording here, noting that John generally uses paidia for children, whereas here teknon is used, which tends to be used of him for general address. John is being careful - as we ought to be - to ensure that the rule of faith is not obscured. Having spoken of good works, he reminds us of faith's rule to keep us from wandering astray. The forgiveness of sins is the foundation without which our religion would be nothing. Nothing so inspires a proper reverence for God than the realization of His work of grace in us, which doesn't freeze our will to do well, but rather inspires us to comply to God's will. John also makes clear the one sole means by which that forgiveness is made available, to prevent us from turning to false hopes and methods of appeasing God. "For as many means of deserving pardon we intrude on God, by so many obstacles are we prevented from approaching Him."
2:13
John moves now to address the three ages of life, lest any should feel excused from the message at hand. The old excuse themselves as beyond learning, the young refuse to learn because the time is not yet, and the middle aged are distracted by other pursuits. To the old he points out the age of the gospel and its eternal author - in effect saying that if they prefer the 'way things were', then they ought to love Christ, who has always been as He is and as He will be. (Heb 13:8 - Jesus is ever the same.) In noting the antiquity of our faith, we also must be careful to discern it's true foundation. He reminds the young men - who tend to be distracted by their youthful strength - that Christ is the source of that strength; that they are strong because of the battle - which battle is won from the start because of Christ. Children find the gospel fit because it points them to the Father. What has been applied to each age separately applies equally to all. We are all orphans without God, we are all weak without His strength, we are all blessed to remember that He is forever the same.
2:14
Calvin thinks this is likely an editor's error, but there is nothing to support the claim. In part, he seems to think thus to justify his reading of v12. Seeing that as a general address followed by three specific addresses, he must here see a spurious verse, or there ought be another reference to children.
 
 

Matthew Henry

2:12-2:14
Given what is to come in the letter, John moves to remind his readers - by their degree of religion - that they must not love this world. As a wise pastor, he distributes his message in a variety of ways suitable for each group of hearers, admonishing all to their common duties of love for each other, and contempt for the world. The novices are reminded of their forgiven state - which reminder serves well for the rest - and being reminded of such, they are reminded to relinquish this world's hold on them as it interferes with God's love. The novice also is reminded that they know their true Father (Heb 8:11 - all shall know the Lord.) Now, John moves to the elders so that the young men can benefit from both preceding messages. Even the oldest disciple requires further teaching, none are too old to learn. He commends them for their advances in the wisdom of God, thereby reminding them not to expect too much for their own account, as it's God's doing. Knowing the source of their wisdom should suffice to weaken their hold on this world. (Phil 3:8 - knowing Christ, all else is loss.) The young adults are reminded that by Christ's training they have vanquished the enemy, and may now apply that training to vanquishing the world's grip. Since they tend to glory in their strength, he reminds them that their strength is in Christ, that they may glory in Christ, and apply His grace to overcoming the devil and the world. Their strength is maintained in that they abide in His word, and it in them.
 
 

Adam Clarke

2:12
Children may refer to John's own converts, or be applicable to all young converts - all who call God Father by the Holy Spirit, whose sins are forgiven on account of Christ Jesus.
2:13
Fathers may refer to those who had chosen Christ at His earliest mention in the region, those who perhaps had personally heard Jesus and thus known him from the beginning. It may, alternatively, refer to Christ's eternal nature. The young men were well-grounded in truth and past any fear and doubt - at the 'zenith of their faith and love.' Children is a different term here, and their state is declared differently. Clarke sees four states: 1) Fathers - who converted very early, and had seen Jesus; 2) Young men - in the prime of spiritual life, fighting under Christ's banner, and overcoming by His blood; 3) Little children - relatively new to faith, yet able by the Spirit to cry out to their Father (this the v13 children); 4) Beloved children - new to faith, and young, these were particularly dear to John, who reminds them of their forgiven state. Within God's earthly family, these four states declare a progression in holiness: teknia - just born to the family, paidia - now able to walk and call their Father by name, neaniskoi - grown to man's estate and able to do the most difficult labor and fight the fight, pateres - those at the foundation, knowing the fullness of God, most filled with wisdom and experience. These answer to the stages of human families: the infant, the child that can speak a bit, the older children who now work, take instruction well, and may be called to defend their family, and the parents who govern.
2:14
Not only have we learned and understood doctrine most completely, but it is the form by which our life is molded - His truth our power and joy, and our lives a constant testimony to that abiding power.
 
 

Barnes

2:12
There is no evidence to support the idea that a portion of these verses are scribal error. He merely wants to personalize his message to each different class. In speaking of his writing, he refers to this letter, and now offers reasons specific to the three classes for bringing this message to them. Both forms of 'little children' are used with the same sense, providing a double reference to three classes. 'Little children' should be taken literally because (a) that is its usual meaning, (b) it fits the progression of age shown in the other two terms, (c) it fits John's style and nature (Jn 21:15 - having recorded Jesus' injunction to feed his [little] lambs, he would recall and apply that injunction), (d) it balances the doubling of reference to each class. It would appear that there were very young children in John's church at that time, although their exact age is not apparent. However, they were clearly under 20, since the next term - neaniskoi - generally applies to the age bracket of 20 to 40; were apparently quite young - there being no fixed rule for an age of admittance into communion in the church; they were thus brought to the special attention of the pastors as the future hope of their church - those who would soon take hold of the reins of power, and were thus most necessarily to be trained up in true religion. He writes to the children because they are forgiven, and as such ought to be exhorted to a holy life. Since our past sins are blotted out, we ought to be holy - being obliged to God for His mercy.
2:13
Now John addresses the over 40 crowd - including the family heads. He speaks to those who through long standing in Christian doctrine knew well its duties. Some may have known Jesus personally, as John had. In either case, their deep understanding gives reason to calling on them to maintain the true doctrine against error. Young men addresses the 20 to 40 age group consistently in scripture. (Mt 19:20-22 - the young prince, Mk 14:51 - the young man that lost his linens, Mk 16:5 - the young man sitting in the tomb, Lk 7:14 - the young man restored to life, Ac 2:17 - visions given to the young men, Ac 5:10 - young men carry out Sophira's body.) These are quite properly called upon to use their strength in the service of promoting religion, and are exhorted not to disgrace the gains made so far in their lives. So three divisions: youths who are forgiven but not yet in service, fathers of long experience to maintain steadfast example, and young men to exert their vigor in the cause of religion. Now we move from the 'I writes' to the 'I have writtens.' This is not a reference to some other letter, but John shifting mental gears from why he wrote the specific thoughts he was writing at that moment, to why he decided to write to them in the first place. The sameness of purpose within the shift of focus shows that John worked deliberately from a deep sense of duty to his flock. To the children, he adds as reason for writing their youthful conversion, and urges them to a life of faith.
2:14
The purpose for writing to the elders remains the same, he moves to exhort them to steadfast adherence. Young men, on the other hand, are given additional reasons why they deserve his attentions: they are strong - and thus fit for active service; and they had shown themselves firm in the face of temptations, not being seduced by error.
 
 

Wycliffe

2:12
This is a general address to all John's readers, pointing out the kinship given them in their common forgiveness of sins through belief in Christ.
2:13
Addressing the elders, he points out that they have come to know Christ as they have abided in His commandments. The younger men have overcome in a fashion which has continuing impact. The evil overcome would appear to be familiar to his readers. Again, children addresses the whole group. John's viewpoint shifts from the letter as to be written to the letter as a finished work. In speaking of their Father, he reinforces the idea of their subordination.
2:14
The young men overcame because they did the will of God as revealed in His word.
 
 

Jamieson, Fausset & Brown

2:12
Another vote for this being a general address - all are little sons and daughters. (Jn 13:33 - Jesus addresses the apostles as little sons, Jn 21:5 - and as little children.) All of God's children enjoy the privilege of forgiveness of sins.
2:13-2:14
The shift in point of view is one from the author's view to the readers'. The elders have known, and do now know Christ. Fathers are characterized by knowledge, young men by activity. Fathers know Christ, whereas children know the Father, this being the first thing children realize. However, they couldn't come to know the Father without the Son (Mt 11:27 - only by the Son's revelation do we know the Father.) The young men overcome not by their own strength but by the strength of God (Heb 11:34 - faith made the weak strong, Jn 16:33 - Christ has overcome the world.) To overcome like Christ, we must be willing to part with the world like Christ. Their strength lies in the Word united with the abiding presence of the Holy Spirit within. (Isa 40:30-31 - physical strength fades, but godly men are renewed with spiritual strength.) There's an interesting story here about John's work with one particular young man after returning from Patmos - apparently taken from Clemens.
 
 

New Thoughts

The connection to the remainder of the letter seems a little clearer now; that he explains his reasons for writing and the reasons why his readers ought to give it their attention. As to the issue of ages here - I still tend to hold to the three ages view. If the address to the youngest seems to fit all, it is simply because none progress to adulthood without having been born a child. Thus what is true of the child, has been true for all - and in this case remains true for all. In contrast, the characteristics of the young man are unique to that group, and are a past memory to the elder. The strength of the elders lies in a different place - not in their victorious power in battle, but in their abiding peace and their breadth of knowledge in the things of God. Each of these retains the forgiveness which constitutes their birth. Each will progress to, be, or have progressed to strong service in God's purposes - given attention to His commandments. One can see the addresses to younger ages serving to remind the older ages of their foundations, and the addresses to the older acting as incentives to the growth of the younger in faith and service. Are these declarations of the ages of growth in love? Yes. At the same time, they are reminders to those at the various stages of what has been and what is to come in their spiritual life. They are - as Matthew Henry points out - reasons to let go the world, and to break its hold upon us, whatever the stage of our Christian walk.