2 Corinthians 4:1-6 meaning

Paul begins Chapter 4 with a conclusion of what he has stated previously, beginning with Therefore connected with we do not lose heart. His assertion following the earlier chapters is that in spite of opposition he has faced and the questions about his authority as an apostle, Paul and his fellow ministers do not lose heart because they know they are following Christ in their ministry, and they can see the positive impact of their ministry through the lives of the Corinthian believers. 

In the previous chapters, Paul asserted the legitimacy of his authority as a minister of Christ to the Corinthians. We can infer these statements are a defense to attacks made against him. Paul asserted:

• He is not a peddler of the gospel by making money a first priority, as are others (2 Corinthians 2:17). 
• He does not need letters of commendation from men, because the Corinthians themselves are his letter of commendation (2 Corinthians 3:2-3). 
• He uses great boldness of speech, not veiling the glory of God as Moses did, but making it manifest to those to whom he ministers (2 Corinthians 3:12-13). 

Now he makes a statement asserting that his goal is not to impress other people, but to live in a manner that honors Christ and reflects the truth of God, which is why in spite of attacks against him he does not lose heart:

Therefore, since we have this ministry, as we received mercy, we do not lose heart, but we have renounced the things hidden because of shame, not walking in craftiness or adulterating the word of God, but by the manifestation of truth commending ourselves to every man's conscience in the sight of God (vv 1-2). 

Paul begins the Therefore statement by saying since we have this ministry. The Greek word translated as ministry can have meaning spanning a spectrum from "waiting on tables" to giving one's life in the service of Christ. In this context Paul refers to the ministry of bringing the gospel to the Gentiles (Acts 9:15, Galatians 1:15-16). 

Paul adds the qualifier as we received mercy to his description of his ministry to the Gentiles. The phrase we received mercy translates a single Greek word "eleeo." This likely refers to the event of Jesus appearing to Paul while traveling to Damascus and calling him to repent and follow Him, as well as calling Paul to cease persecuting the church and turn to serving the church (Acts 9:3-5, 15). 

Paul uses "eleeo" to refer to his conversion in his first letter to Timothy, saying that "Christ Jesus came into the world to save sinners, among whom I am foremost of all." But Paul says Jesus granted him "mercy" ("eleeos") so that He could use him as an example of His redeeming power (1 Timothy 1:13, 15-16). Paul received mercy to be redeemed as well as to be given the ministry to bring the gospel to the Gentiles. When Paul received his commission to be a minister to the Gentiles, he was called to suffer to the sake of Christ (Acts 9:15-16). 

Since Paul has this ministry from God, granted by His mercy, Paul says we do not lose heart. Even though some of the news Paul has received from Corinth has been discouraging and some of the hardships he describes in 2 Corinthians 4: 8-9 are rather daunting, based on the ministry he has received through mercy, he can confidently say we do not lose heart. By using we, Paul is probably including those who have ministered with him, particularly Timothy who is introduced as a co-author (2 Corinthians 1:1). 

Paul now expands on a reason he and his fellow ministers have not lost heart: But we have renounced the things hidden because of shame. Paul explains what he means by this in his next phrase, asserting that he is all about Christ and he will not rely on any human ways or manipulations in his declaration of the gospel. He describes the things he has renounced as: Not walking in craftiness or adulterating the word of God. 

In Chapter 2, Paul referred to those who were "peddling the word of God" (2 Corinthians 2:17). It seems likely that Paul is referring here to the same sorts of people who are self-seeking, posing as ministers of the gospel but actually walking in craftiness and misusing the word of God. 

Paul repeats the Greek word translated craftiness ("panourgia") later in this letter to describe how Satan deceived Eve (2 Corinthians 11:3). The word translated adulterating is rendered in some translations as "deceitfully" or "distort." This craftiness is worldly and self-seeking. Jesus admonished His disciples to be shrewd as serpents but innocent as doves (Matthew 10:16). There is a way to be shrewd in a godly manner. Jesus perceived the craftiness of the Pharisees and one-upped them in shrewdness, as we see in this story from Luke:

"But He [Jesus] detected their trickery ["panourgia"] and said to them…" (Luke 20:23). 

Paul here uses the term "panourgia" to apply to adulterating the word of God. Paul does the opposite. He uses wisdom to advance the word of God. 

Paul is asserting that his ministry to the Corinthians is not a self-serving peddling of the gospel for financial gain. He is not telling people what they want to hear in order to gain money or influence. He is telling them the way to live constructively through faith; believing God's ways are for our best. This is shrewd in a godly manner because Paul is laying up for himself eternal blessings at the judgment (2 Corinthians 5:10). Paul will call this "an eternal weight of glory" (2 Corinthians 4:17). 

Paul desires that the believers in Corinth walk in the power of Christ to overcome sin and the flesh in their lives, and gain the greatest fulfillment from life, apart from the ways of the world (Galatians 5:16, 6:8). The further inference is that those who brought sorrow to the Corinthians were the self-seeking posers walking in craftiness like Satan or adulterating the word of God for monetary gain (2 Corinthians 2:17). 

In his last letter prior to his death, Paul tells Timothy to watch for those who desired to "have their ears tickled" and who desired to "accumulate for themselves teachers in accordance to their own desires" (2 Timothy 4:3). This would be like someone adulterating the word of God. Paul is warning his protégé to avoid becoming like the false ministers who affected Corinth. 

Paul has seen it before, and knows it is a temptation to be watched and avoided. In his first letter to the Corinthians, Paul asserts that the reason he did not accept financial support, but paid his own way, was to help himself avoid abusing his authority in the gospel (1 Corinthians 9:18). He also noted the existence of self-serving ministers in his letter to the Philippians (Philippians 1:15-16). 

Paul recognized fully that he could also become self-seeking if he had not renounced such behavior. In saying this, he provides an example of taking action against his own flesh. He does not say "I would never do that." Instead, he recognizes his own sin nature, and proclaims that he has renounced such behavior. In doing this it is inferred he invites examination, and indeed he had substantial examination of himself and his ministry (1 Corinthians 4:3-5, 9:3). 

Later in this letter, Paul encourages the Corinthians to follow his example and examine themselves (2 Corinthians 13:5). The point is to self-reflect, recognize sin and confess so that it will be forgiven (1 John 1:9). The objective of such self-reflection is to repent (change behavior) in order to avoid the adverse consequences of sin (Romans 1:24, 26, 28) and loss at the judgment of Christ (1 Corinthians 3:14-15, 2 Corinthians 5:10). 

Paul contrasts those adulterating the word of God with his own approach, saying he ministers by the manifestation of truth commending ourselves to every man's conscience in the sight of God (v 2). Those adulterating the word of God seek advantage of earthly gain for themselves by exploiting others. But Paul's goal is to manifest truth. The verb form of the Greek word translated manifestation appears in the famous passage in the Gospel of John, where Jesus speaks to Nicodemus, along with the same Greek word translated here as truth:

"But he who practices the truth comes to the Light, so that his deeds may be manifested [verb form of manifestation] as having been wrought in God."
(John 3:21) 

This verse sheds light on what Paul means when he speaks of manifestation of the truth. Paul's deeds show evidence that he is walking in the truth of God's word, which means he is walking in love toward others. This contrasts directly with exploiting others. 

The word manifestation emphasizes that Paul claims openly that he is willing to be observed and held accountable for his actions. That is why he follows his proclamation that he ministers by the manifestation of the truth by inviting others to judge his deeds, saying that in taking this stance he and his co-ministers are commending ourselves to every man's conscience in the sight of God, which means he is willing to stand judgment before every man's conscience. 

As a way of holding himself accountable, Paul is applying to himself the principle that Jesus taught in His Sermon on the Mount, when He said of teachers: "you will know them by their fruits" (Matthew 7:20). According to Jesus's illustration good teachers are like good trees—they both bear good and life-giving fruit. False prophets are toxic and are like bad trees that bear rotten fruit that corrupts much that is around them (Matthew 7:15-20). 

Jesus was warning His followers to not follow bad teachers, and the way that His followers could discern if a teacher was bad was to look at the fruit or byproducts of that teacher's life. Paul was calling upon the Corinthian believers to examine the teacher's life and discern for themselves to see if he was a good, life-yielding teacher. 

In making his comparison, Paul does not appeal to a human standard. He does not compare himself to others. He appeals to the conscience of each person in the sight of God. Ultimately Paul works for God's approval (Colossians 3:23; 2 Corinthians 5:10). But here he also expresses a willingness to be evaluated by each person's conscience. 

In Chapter 1, Paul referenced his conscience as being a testimony to his integrity. Paul refers to the importance of the conscience a number of times in his letters to the Corinthians, and places a high importance on examining our consciences, keeping our consciences clear, protecting the consciences of our brethren, and listening to our conscience (see commentary on 2 Corinthians 1:12-14). 

And even if our gospel is veiled, it is veiled to those who are perishing (v. 3). Paul continues to speak of the gospel presented by him and his co-author Timothy (and perhaps others, expressed as our gospel). He refers again to the imagery from the veil of Moses, which he says lies over the hearts of those who do not comprehend the gospel of grace in Christ because they are blinded by the veil of the law (2 Corinthians 3:14-15). Paul declared of his ministry "we preach Christ crucified, to Jews a stumbling block and to Gentiles foolishness" (1 Corinthians 1:23). Jesus was a "stumbling block" to Jews who are blinded by their adherence to religious rules and laws (Romans 9:31-32, 11:25). 

This apparent conflict between Paul's gospel of grace and an adherence to law is consistent with the political fights he had with competing Jewish "authorities" as chronicled in other letters he penned. An example is Romans, where Paul answers a charge against him that he calls slanderous (Romans 3:8). The charge is that his teaching of salvation by grace through faith (that Jesus's death on the cross is sufficient) led to a false accusation that if Paul's teaching is true, then believers ought to sin (have more "fun") and do God a favor (increase His grace). Paul asserts that our sin does cause God's grace to abound (Romans 5:20). However, sin is not "fun"—rather it leads to death, slavery, addiction, and loss of mental health (Romans 6:23, 16, 1:26, 28). 

When Paul speaks of the gospel he includes the entire scope of the good news of Jesus, which includes a past, present, and future salvation. Salvation means "something is delivered from something" and context determines what is being delivered from what. In the case of the use of the word gospel, Paul typically uses it to span the entire spectrum of deliverance, as he uses it in Romans:

"For I am not ashamed of the gospel, for it is the power of God for salvation to everyone who believes, to the Jew first and also to the Greek. For in it the righteousness of God is revealed from faith to faith; as it is written, "BUT THE RIGHTEOUS man SHALL LIVE BY FAITH."
(Romans 1:16-17)

We see in this usage from Romans that the gospel has the "power of God for salvation" through faith. But that spans "from faith to faith" indicating that the salvation being contemplated is faith from beginning to end. This of course implies that there is a story with a beginning and end. In this case, the story is that of our life. Our life as a new creation in Christ begins when we believe, and continues until we are glorified by receiving a new, resurrected body. 

Thus, we would expect, and in fact find, that "salvation" appears in three tenses: past, present, and future. 

• Past: That Jesus gives a new spiritual birth to those who believe (John 3:3, 14-16, 2 Corinthians 5:17). This is a once-for-all new birth that delivers us from being separated from God, and is in the past for any believer. 
• Future: That we can all look forward to a time when we will be delivered from the presence of sin and receive a new, resurrected body, as indicated in Romans 13:11, which says as we get further from when we first believed (past salvation from the penalty of sin), we are getting closer to salvation (deliverance from the presence of sin). 
• Present: That we can be delivered from/walk apart from the power of sin in our daily lives, avoiding its negative consequences. This is as in Philippians 2:12, where Paul exhorts them to "work out" their salvation, because defeating sin in our daily lives requires an active walk of faith ("from faith to faith"). 

We can infer from the context that those who are perishing are those who have been blinded through unbelief. This could apply both to the past and present application of the gospel, or of "salvation." 

For the "past" application, we could apply the phrase those who are perishing to those who have never believed on Jesus. In this application we can take the phrase are perishing to refer to an ongoing process of an unbeliever experiencing the adverse consequences of sin while looking ahead to the inevitability of death, when their opportunity to believe has passed and they are forever separated from God in the lake of fire because their name is not written in the Book of Life (Revelation 20:15). In this sense, all who are apart from Christ are in a perpetual and escalating circumstance of perishing. 

However, since the phrase those who are perishing implies ongoing action, Paul could have in mind the application of the present-tense of "salvation" that refers to the power of the Spirit to deliver believers from the adverse consequences of the flesh and from sin when we walk by the Spirit according to faith (Galatians 5:16, 6:8). Perhaps he has in mind the competing ministers who exploit others rather than serving in love. They would be perishing in a number of ways. For example their consciences would sear (1 Timothy 4:2), they would bear the fruit of the flesh (Galatians 5:19-21) and they would experience a life of biting and devouring rather than teamwork and harmony (Galatians 5:15). 

In either case, the problem is one of choosing a wrong perspective, as Paul asserts with the phrase: In whose case the god of this world has blinded the minds of the unbelieving so that they might not see the light of the gospel of the glory of Christ, who is the image of God (v 4). 

We know believers can be blinded by Satan, who is the god of this world (John 14:30). Jesus addressed Satan by speaking directly to Peter, indicating that at that moment Peter was doing the bidding of Satan (Matthew 16:23). This was shortly after Jesus said Peter was blessed and He would build His church upon Peter (Matthew 23: 17-19). Therefore, we know Peter was a believer when Jesus said to him, "Get behind Me, Satan." This is why believers need to seek to gain a renewed mind in order to escape being conformed to the world (Romans 12:2).

We also are told to resist the devil and he will flee from us (1 Peter 5:8-9). We are told to take up the "shield of faith with which you will be able to extinguish all the flaming arrows" of Satan (Ephesians 6:16). Since the "flaming arrows" are contending with the "shield of faith," and faith is decided in the mind, we can infer that Satan's "flaming arrows" are intended to blind people's minds so that they will not believe. 

When any person, including a believer, has their mind blinded, then they will not see the light of the gospel of the glory of Christ. The light of the gospel in v 4 is the same as the truth spoken of in v 2. When we have our minds blinded, we are unable to see the truth. We are only able to see what is true when we begin with faith. 

This is because faith in God's perspective of the world is the essential foundation for seeing what is true. The fear of the Lord is the beginning of knowledge (Proverbs 1:7). When we rely on our own reason and experience as a foundation for knowledge, it inevitably leads to folly and madness (see commentary on Ecclesiastes 2:12-17). 

Paul is referencing Satan and his influence in this world. 1 John 5:19 says, "the whole world lies in the power of the evil one." The Apostle John also says, "Do not love the world nor the things in the world" (1 John 2:15). This infers that we have a basic choice whether to love the things in the world, which are temporal, or to love the things of Christ which are eternal. The values, desires, and "rewards" of this world can blind our minds to the true message and calling of Christ. The true calling of Christ is that He desires us to share in the glory of Christ through our service in the obedience of faith. 

Jesus has restored the right of humans to reign in harmony with God and one another in the earth through His obedience to death on the cross (Hebrews 2:5-10). In doing this, Jesus was rewarded as the "Son" of the earth, the firstborn with the right to reign (Hebrews 1:5, 8, 13, Matthew 28:18). Jesus desires to bring "many sons to glory" and share His reign with those who overcome as He overcame (Hebrews 2:10, Revelation 3:21). This is likely what Paul has in mind when he uses the term glory of Christ. It is also likely what Paul has in mind when he speaks of a future reward for faithfulness that is an "eternal weight of glory" later in this chapter (2 Corinthians 4:17). 

The light of the gospel of the glory of Christ is a contrast with the glory offered by the world. The glory of the world is empty and fleeting, while the glory of Christ is eternal. We can consider that the path of least resistance in this fallen world is to choose to love the things of the world, things that are passing away (1 John 2:15-17). However, scripture exhorts us to love God and follow His ways. Rather than the empty promises of the world that pass away, when we love God we gain rewards that are beyond our comprehension, as Paul explained in his first letter to the Corinthians (1 Corinthians 2:9). 

That those who are blinded by Satan might not see the light of the gospel of the glory of Christ calls to mind the words of Jesus in Matthew:

"The eye is the lamp of the body; so then if your eye is clear, your whole body will be full of light. But if your eye is bad, your whole body will be full of darkness. If then the light that is in you is darkness, how great is the darkness!"
(Matthew 6:22-23)

So, when Paul says the god of this world has blinded the minds of the unbelieving, he is talking about the focus of our minds being on gaining the rewards of this world. If we "love this world" as John says, then the light within us is really darkness, or the veil as Paul would describe it. We are unable to see the goodness God has for us. Rather, we see the empty promised rewards of the world as life, when they are actually death. 

Paul continues contrasting his own ministry that pursues truth with the disingenuous ministers walking in craftiness who are twisting the gospel for their own gain: For we do not preach ourselves but Christ Jesus as Lord and ourselves as your bond-servants for Jesus' sake (v 5). 

Again, Paul is declaring his focus on Christ and his dependence on Christ. He declares that by preaching Christ Jesus as Lord, Paul and his co-ministers are the Corinthians' bond-servants for Jesus' sake. Paul's goal is to serve and benefit the Corinthian believers. He does so by exhorting them to follow his example, and walk in obedience to Christ, even as he faithfully walks in obedience to his calling from God by preaching the truth of God (1 Corinthians 9:16). As we will see in 2 Corinthians 11:25-29, Paul paid a heavy price for speaking the truth. He will ultimately lose his life for being a faithful minister of Christ. 

This ministry and the preaching of the gospel has only one purpose; that the followers of Christ might see the light of the gospel of the glory of Christ, who is the image of God. When Paul uses the phrase Christ Jesus as Lord, he is declaring that Jesus is the Christ, the Messiah, the Anointed One, and as Lord, the resurrected, risen Lord. The words in this line are instructive:

• Christ means anointed—Jesus is the anointed messiah to take the throne of David as well as taking the throne of earth. 
• Jesus means "Yahweh is salvation," and is the name God chose for His sent messiah. 
• Lord means the one in authority. Because of His faithful obedience to death on a cross, Jesus was granted all authority over heaven and earth as the God-man (Matthew 28:18; Philippians 2:9-10). 

That Paul says Jesus is the image of God likely focuses on Jesus's fulfillment of the prophecy that God would send a prophet like Moses who would speak directly the word of God but be human, so the people could hear and not fear (Deuteronomy 18:18). In this respect, Jesus was seen as human by people around Him, while being fully God. Thus, as the image of God, Jesus is fully God (John 1:1, Hebrews 1:8). 

We can see this in Paul's letter to the Colossians, where he uses the same Greek word translated in verse 4 as image. In this verse, the description of Jesus is clearly synonymous with the biblical description of God as the creator and sustainer of all things who was in the beginning (Genesis 1:1):

"He [Jesus] is the image of the invisible God, the firstborn of all creation. For by Him all things were created, both in the heavens and on earth, visible and invisible, whether thrones or dominions or rulers or authorities—all things have been created through Him and for Him. He is before all things, and in Him all things hold together."
(Colossians 1:15-17)

Paul asserts that in teaching them the truth rather than tickling their ears and fleecing their wallets, he and his ministry companions present ourselves as your bond-servants for Jesus' sake. The Greek word translated as bond-servants is "doulos" and can equally be translated as "servants." A servant is one in the service of a master, who is obligated to obey the instructions of that master. 

So Paul is saying that he and others (ourselves) are servants to the Corinthians, but not to do whatever the Corinthians tell them, but rather for Jesus' sake. They are the servants of Jesus who are serving Him by teaching the Corinthians the truth. Teaching them the truth included pointing out false teaching that brought sorrow, but was necessary for their proper instruction (2 Corinthians 2:5-6). 

Paul also uses "doulos" (bond-servants) in regard to Jesus in Philippians 2:5-7. Jesus was a servant to humanity by following in obedience to His Father:

"Have this attitude in yourselves which was also in Christ Jesus, who, although He existed in the form of God, did not regard equality with God a thing to be grasped, but emptied Himself, taking the form of a bond-servant, and being made in the likeness of men."
(Philippians 2:5-7)

Even though Paul says ourselves as your bond-servants, he makes sure that he adds for Jesus' sake. Even though he declares himself as a servant to the Corinthians, he does not belong to them, rather he belongs to Christ. Everything Paul does as a servant is for Jesus' sake and at His bidding. 

Paul returns to the theme of the glory of God shining through the face of Moses being like the glory of the gospel shining through the lives of his faithful followers in Christ saying:

For God, who said, "Light shall shine out of darkness," is the One who has shone in our hearts to give the Light of the knowledge of the glory of God in the face of Christ (v 6).

God is the creator of all things. One of His first creative acts recorded in scripture was to bring light to shine out of the darkness, meaning to create light where there had been none before:

"Then God said, 'Let there be light'; and there was light" (Genesis 1:3). 

Another translation renders verse 6 as "For it is the God who commanded light to shine out of darkness." The light shone because God decreed for it to shine. That same powerful God is the One who has shone in our hearts through making us new creations in Christ and giving us the indwelling Holy Spirit (2 Corinthians 5:17). John introduces Jesus in his Gospel by describing Him as "the true Light which, coming into the world, enlightens every man" (John 1:9). 

Light is good. Light enables life to survive. Light is a common metaphor for truth. Light illuminates. It reveals reality and brings clarity. Light enables men to see the world around them. Light shines and shows things for what they are. In so doing light can be a purifying element because it helps us see what needs cleaning or is out of place. 

John also writes: "God is Light, and in Him there is no darkness at all" (1 John 1:5b).

Paul says that God, the Creator of light, is the One who has shone in our hearts, he is saying God revealed Himself and has poured Himself into his and the Corinthian believers' hearts. God and His light dwells within their hearts. God's truth and holiness and life has shone within every believer. And it first shined into their hearts when they believed and received the Gift of Eternal Life. 

Interestingly, Paul had God's blinding light flash around him (and into his heart) at his spectacular conversion on the road to Damascus (Acts 9:3-5). 

Just as each believer is a "letter of Christ" because he wrote it on their heart, Jesus has shone in our hearts (2 Corinthians 3:3). The God who created the world is the same God that created a new heart within each believer (2 Corinthians 5:17, Ezekiel 36:26-27). 

God has a specific application for each person who He makes into a new creation—to give the Light of the knowledge of the glory of God in the face of Christ. Most translations do not capitalize Light. The knowledge of God is what turns darkness in our hearts into light. It is also true that Christ dwells within us, and the Holy Spirit leads us into all truth (Romans 8:9-11). 

Paul's phrase the knowledge of the glory of God means intimate, relational, familiar knowledge. The Greek word translated as knowledge in this verse is a form of "gnosis." "Gnosis" means "experiential or relational knowledge" as contrasted with the other primary Greek word for knowledge—"oida." "Oida" describes theoretical understanding or "book knowledge." God transmits to our hearts real, experiential knowledge of Himself through Christ. 

When Jesus described eternal life as knowing God, John used the verb form of "gnosis" to explain it (John 17:3). Paul is saying that we have a personal knowledge of God's incredible glory as we see the face of Christ. Moses was given the immense privilege to see the glory of God's back (Exodus 33:20-23). New Testament believers have an even greater privilege, which is to see the face of Christ by faith through the Spirit. Thus in our hearts we can have intimate knowledge of God's glory. 

The reference of the glory of God in the face of Christ again hearkens back to Paul's illustration of Moses having been in God's presence which caused his face to shine (2 Corinthians 3:13-14). Moses put a veil over his face because the people feared his shining skin (Exodus 34:30, 33). Paul likens himself and other faithful believers as being like the witness of Moses in showing forth God's glory, but with the veil removed. 

A reasonable application of this is that any believer lives as a faithful witness when they show the Light of the knowledge of the glory of God in the face of Christ to onlookers. The Light seen by others through the faithful witness of His people comes from the knowledge of the glory of God in the face of Christ. Just as Moses' face glowed from being in God's presence, people should see the face of Christ in our own face because we reflect the knowledge of the glory of God in the way we live. 

This bears repeating: other people should see God's glorious light when they see us and how we love and serve others. They should see His goodness, His love, His wisdom, His grace in our actions, words, and attitudes. Beautiful sunrises, rapturous music, amazing creatures, all display the glory of the Creator (Psalm 19:1-2). But as redeemed image-bearers of the Creator, nothing on earth should radiate God's glory and goodness more faithfully than believers—save Christ alone. 

The glory of God is seen by the entire creation (Psalm 19:1-4, Romans 10:18 which quotes Psalm 19:4). The glory of God is also observed when God's character and essence is revealed to onlookers through His people. When believers abide in Christ and follow His ways, they show God's character to onlookers and thereby show God's glory (John 15:8). 

There are numerous references, particularly in the New Testament, about light piercing, penetrating, or dispelling the darkness (John 1:4-5, 7-9, 3:19-21). In addition to referring to the creative account, Paul may be thinking of his own experience of encountering the light:

"As he [Paul] was traveling, it happened that he was approaching Damascus and suddenly a light from heaven flashed around him."
(Acts 9:3)

That light seen by Paul was the light of Christ and forever changed him. Paul was jolted out of deception (darkness) and into the light (truth). He endeavored for the rest of his life to follow that light. He continues, saying that this light of Christ is the One who has shone in our hearts. Paul may be recalling his own conversion experience and referring to all who come to Christ as ones in whom the light of Christ shines. The picture is of the light of truth coming into our hearts and replacing the darkness of sin (1 Corinthians 4:5). The light of God is the love of God (Colossians 1:13). 

Light dispelling the darkness, particularly as it relates to conversion, is a common theme throughout the New Testament (John 1:5, Acts 26:18, Ephesians 5:8, Colossians 1:12-13, 1 Thessalonians 5:4-5, 1 Peter 2:9). This light is the light of a new creation, as Paul says in Chapter 5:

"Therefore, if anyone is in Christ, he is a new creature; the old things have passed away; behold, new things have come"
(2 Corinthians 5:17). 

The description of the light of Christ and the light of the knowledge of Christ shining in our hearts is consistent with the idea that the new creation of our self comes about through the light of Christ. 

Now believers in Jesus have the knowledge of the glory of God within us, because Christ is within us. The glory (Greek "doxa") of something is its essence being seen by an observer. Paul asserts this in his first letter to the Corinthians, giving an example that the sun and moon each have a different sort of glory that can be observed, because they are different sorts of creations (1 Corinthians 15:40-41). The glory of God is the essence of God being observed. Scripture asserts that God's glory is seen throughout His creation (Psalm 19:1-4, Romans 1:20). Since humans are made in God's image, we have a particular opportunity to demonstrate His glory. 

In v 6, the glory of God is shown in the face of Christ. The face of Christ gives the light of the knowledge of the glory of God into our hearts. In v 4, the the glory of Christ, who is the image of God, is shone forth into the hearts of believers through light of the gospel of the glory of Christ. The word gospel means "good news" and therefore indicates that this knowledge and understanding of light comes through hearing and believing the truth of God. 

It is inferred that when we hear and believe what is true, our eyes are opened to see God and Christ in ways that were previously veiled (v 4 speaks of "minds" being "blinded" by the "god of this world"). The opening of eyes could include giving us eyes to see what is true all around us. It could include seeing what is true in others. And it could include us shining forth the truth to others when we walk in faith. 

This knowledge likely does not refer to disconnected factual information we might gather or learn—any person has that. What is inferred is that the knowledge of the glory of God within us allows us to see things as they actually are. It allows us to gain a degree of understanding as to how all things fit together. God made all things, and all things reflect Him. As we gain knowledge of the glory of God we would naturally be able to see and make connections about what is true. This is particularly valuable since the truths of scripture are highly paradoxical. 

For example, it initially seems paradoxical that Jesus says that the way to gain the very most from life is through laying aside self and serving others, as He laid aside self and served (Philippians 2:5-10, Matthew 16:24-25). Once our eyes are opened to the reality that the greatest fulfillment in life comes through being connected to a purpose greater than ourselves, this begins to make sense. But we must have eyes to see in order to grasp such truths. We gain such insight through gaining light from the good news of Christ. 

We can now see and know the glory of God in the face of Christ. This infers that the light of truth that shone forth in our hearts can allow us to see and know Jesus. This is enormous, since Jesus said that the greatest fulfillment in life ("eternal life") comes through knowing God and Jesus Christ whom He sent (John 17:3). As we know God and Christ through faith, we grow in our fulfillment in life. 

As Paul referenced the image of Moses's veil in 2 Corinthians 3:18, we likewise can now "with unveiled face" live as unto the Lord before men. We can both show as well as see the glory of God in the face of Christ through the lives of other believers, when they walk in the Spirit and exhibit the glory of God through bearing good fruit (John 15:8).