IN THE POWER OF SIGNS AND WONDERS, IN THE POWER OF THE SPIRIT: en dunamei semeion kai teraton, en dunamei pneumatos (theou): (Acts 14:10; 15:12; 16:18; 19:11,12; 2 Corinthians 12:12; Galatians 3:5; Hebrews 2:4 ) (Matthew 12:28; Acts 1:8; 1 Corinthians 12:4-11; 1 Peter 1:12 )

Keep the context in mind for Paul has just stated...

For I will not presume to speak of anything except what Christ has accomplished through me, resulting in the obedience of the Gentiles by word and deed (see note Romans 15:18) (Comment: John Piper reminds us that "The aim of missions is to bring about the obedience of faith among all the unreached peoples of the world. But that is not the ultimate goal. The ultimate goal—even of faith and obedience—is "for the sake of His name. " The fame of Christ, the reputation of Christ is what burned in the heart of the apostle Paul. The faith of the nations was not an end in itself. It was the way that the name of Christ would be honored. This is what filled him with such a passion for the Great Commission. Jesus had told Ananias "how much he [Paul] must suffer for the sake of My Name" (Acts 9:16). And he had never turned back from his willingness to suffer if only the fame of Christ would result. Near the end of his life he could still say, "I am ready not only to be imprisoned but even to die at Jerusalem for the Name of the Lord Jesus" (Acts 21:13)-- from The Pleasures of God)

Paul's explains how the obedience of the Gentiles was brought about, stating that it was by the power of the Spirit Who provided the inherent ability to perform the signs and wonders.  (signs and wonders were the "deed" he had mentioned in the previous verse)

The NLT paraphrase gives a good sense of the meaning of the original Greek:

I have won them over by the miracles done through me as signs from God--all by the power of God's Spirit.

The power of the Spirit was promised by Jesus to His disciples...

but you shall receive power when the Holy Spirit has come upon you; and you shall be My witnesses both in Jerusalem, and in all Judea and Samaria, and even to the remotest part of the earth. (Acts 1:8)

Paul reminded the Corinthians...

my message and my preaching were not in persuasive words of wisdom (for human words and wisdom would rob the gospel of its power, eg as in an intense, emotional appeal), but in demonstration (setting forth or an exhibition of proof) of the Spirit and of power ("the sense is 'the powerful demonstration of the Spirit'" - Hodge) that your faith should not rest on the wisdom of men, but on the power of God. (1Cor 2:4-5) (Comment: Charles Hodge wrote that "Paul relied, therefore, for success not on his skill in argument or persuasion, nor upon any of the resources of human wisdom, but on the testimony that the Spirit bore to the truth. The Holy Spirit demonstrates the Gospel to be true.")

It has been said that the great American preacher Jonathan Edwards read his sermons expressly for the purpose that he would not be guilty of using persuasive techniques to gain a response. The response he sought was that which was wrought by the the Gospel delivered in power and in the Spirit.

John Stott has written

It seems that the only preaching God honors through which His wisdom and power are expressed is the preaching of a man who is willing in himself to be both the weakling and the fool.

Charles Spurgeon agreed declaring that...

The power that is in the Gospel does not lie in the eloquence of the preacher, otherwise men would be the converters of souls, nor does it lie in the preacher’s learning, otherwise it would consist in the wisdom of men. We might preach until our tongues rotted, till we would exhaust our lungs and die, but never a soul would be converted unless the Holy Spirit be with the Word of God to give it the power to convert the soul.

From the outset of this letter Paul had made it very clear that the effect of the effectiveness of Gospel was directly related with the fact that the

gospel is the power (dunamis = inherent power) of God for salvation to everyone who believes, to the Jew first and also to the Greek (see note Romans 1:16)

Paul relied for success not on his own skill or eloquence, but on the powerful demonstration of the Spirit. In a rhetorical question to the Galatians who were being tempted to work out their salvation in the power of their flesh Paul asked...

This is the only thing I want to find out from you: did you receive the Spirit by the works of the Law, or by hearing with faith? Are you so foolish? Having begun by the Spirit, are you now being perfected by the flesh? Did you suffer so many things in vain-- if indeed it was in vain? Does He then, who provides (epichoregeo = continuously supplies abundantly and with great generosity as did patrons of the arts who underwrote productions of Greek plays) you with the Spirit and works miracles (dunamis = inherent power) among you, do it by the works of the Law, or by hearing with faith? (Galatians 3:2-5)

Paul was so convinced of his weakness and God's power that he said...

I will rather boast about my weaknesses, that the power (dunamis = inherent power) of Christ may dwell in me. (2Cor 12:9b)

Writing to the Ephesians at the end of his great prayer for their inner strengthening, he declares...

Now to Him who is able to do exceeding abundantly beyond all that we ask or think, according to the power (dunamis = inherent power) that works within us (see note Ephesians 3:20)

Writing to the Thessalonians who had been converted under Paul, Silas and Timothy's ministry in Acts 17:1-4, Paul explained that...

our (Paul, Silvanus, Timothy) gospel did not come to you in word only (first, the gospel was proclaimed), but also in power (second, it was proclaimed in power) and in the Holy Spirit (third it was proclaimed in the Spirit) and with full conviction (fourth, they believed the gospel they proclaimed); just as you know what kind of men we proved to be among you for your sake (fifth, they lived among them as examples of the truth they proclaimed). (see note 1Thessalonians 1:5)

Signs (4592) (semeion) refers to what distinguishes one person or thing from another (as in Lu 2:12 below, Ro 4:11). Signs point to something and are a visible manifestation of an invisible reality that may or may not always be supernatural. Another meaning and the one in the present verse is as a reference to a miraculous event contrary to the usual course of nature and intended as a pointer or means of confirmation. 

The angel announcing Jesus' birth appeared to some shepherds staying out in the fields declaring

this will be a sign for you: you will find a baby wrapped in cloths, and lying in a manger. (Lu 2:12)

Luke records Jesus' reply to

the crowds (that were) increasing (saying) "This generation is a wicked generation; it seeks for a sign, and yet no sign shall be given to it but the sign of Jonah. For just as Jonah became a sign to the Ninevites, so shall the Son of Man be to this generation." (Lu 11:29-30)

Semeion is used in the NT some 69 times. Observe that it is most often found in the Gospels and Acts but that there is also a cluster of uses in the last book, Revelation, many of these uses referring to counterfeit signs (Matt. 12:38f; 16:1, 3f; 24:3, 24, 30; 26:48; Mk. 8:11f; 13:4, 22; 16:17, 20; Lk. 2:12, 34; 11:16, 29f; 21:7, 11, 25; 23:8; Jn. 2:11, 18, 23; 3:2; 4:48, 54; 6:2, 14, 26, 30; 7:31; 9:16; 10:41; 11:47; 12:18, 37; 20:30; Acts 2:19, 22, 43; 4:16, 22, 30; 5:12; 6:8; 7:36; 8:6, 13; 14:3; 15:12; Ro 4:11; 15:19; 1 Co. 1:22; 14:22; 2 Co. 12:12; 2 Thess. 2:9; 3:17; Heb. 2:4; Rev. 12:1, 3; 13:13-14; 15:1; 16:14; 19:20)  For discussion of the counterfeit signs see notes on (Revelation 13:13; 13:14; Revelation 16:14; Revelation 19:20)

Jesus'  turning water to wine was the beginning of His signs in Cana of Galilee, where He manifested His glory, and His disciples believed in Him. (Jn 2:11, cf other "signs" by Jesus - his healing of the official's son in Jn 4:54 feeding 5000 Jn 6:14 raising Lazarus Jn 12:18)

Luke records Paul's casting a demon from a slave girl when...

she continued doing this (proclaiming Paul and Silas were "bond-servants of the Most High God, who are proclaiming to you the way of salvation") for many days. But Paul was greatly annoyed, and turned and said to the spirit, "I command you in the name of Jesus Christ to come out of her!" And it came out at that very moment. (Acts 16:18)

And what was the result of this supernatural event? It got Paul and Silas beaten with rods and placed in a dungeon in stocks. But what godless men did for evil, God used for good, allowing Paul to proclaim the gospel to the Philippian jailer and his household, all of whom were saved and who undoubtedly formed a nucleus for the first church in Europe!

Signs per se do not save a man but they do point to the Man in Whom there is salvation -- see especially Jn 2:23-25 12:37 20:30-31.

Paul used sign in this same letter to refer to the sign of circumcision (see note Romans 4:11), referring of course to an external physical act pointing to an inner spiritual reality of heart circumcision (cp note Romans 2:28; 2:29).

In Acts Luke records miraculous signs (actually the word dunamis) writing that...

God was performing extraordinary miracles by the hands of Paul, so that handkerchiefs or aprons were even carried from his body to the sick, and the diseases left them and the evil spirits went out. (Acts 19:11-12)

Then Luke records the ultimate result of the supernatural power was that...

the word of the Lord (the Gospel of God) was growing mightily and prevailing. (Acts 19:20)

Middletown Bible has a summary of some of the miracles Christ accomplished through Paul...

What were some of the miracles accomplished by Christ through Paul?

Acts 13:6-12 Elymas the sorcerer struck with blindness

Acts 14:1-3 Signs and wonders done by their hands

Acts 14:8-10 A man crippled from birth instantly healed

Acts 16:16-18 A demon cast out of a certain damsel

Acts 16:25 ff. Miraculous deliverance from prison

Acts 19:11-16 Many healed and demons cast out

What were the results of the miracles?

"Then the deputy, when he saw what was done, believed, being astonished at the doctrine of the Lord" (Acts 13:12).

"And fear fell on them all, and the name of the Lord Jesus was magnified...So mightily grew the Word of God and prevailed" (Acts 19:17,20).

Wonders (5059) (teras) are similar to signs but appeal to the senses, being recognized as a phenomenon that needs to be explained.

Teras is derived from the verb tereo which means to keep, watch and thus conveys the idea of something which due to its extraordinary character is apt to be observed and kept in the memory. It is a miracle regarded as startling, imposing or amazing. Teras refers to  “something strange",  a phenomena which compels one's attention and causes one to "look again" or causes the beholder to marvel. Teras is always in the plural and always translated “wonders.”

In short, signs are intended to appeal to the understanding and “wonders” to the imagination.

Someone has said that signs and wonders are like the finger prints of God, valuable not so much for what they are as for what they indicate of the grace and power of the Doer. Before the full gospel message was recorded in what we now call the New Testament, God often used signs and wonders to authenticate true preaching and teaching. The ministry of the apostles, especially in the earliest days of the church, was accompanied by authenticating miracles.

Charles Hodge says

They are called signs because they are evidences of the exercise of God’s power and proofs of the truth of his declarations, and miracles because of the effect which they produce on the minds of men.

Divine affirmation does not require miracles. In fact, much and perhaps most of Paul’s own ministry was not affirmed in such dramatic ways. But the power of the Spirit is always evidenced in some way when the gospel is proclaimed, even by the simplest and most uneducated preacher who seeks to glorify Christ. In fact the most miraculous authentication (establishment of the genuineness) of the gospel is not the physical signs and wonders accompanied it but the opening of blind eyes so that they are turned "from darkness to light and from the dominion of Satan to God" (Acts 26:18). The power of the gospel is authenticated by the transformed lives it produces.

John Courson has this to say regarding the miraculous reminding us that...

the Holy Spirit is like steam in a locomotive. He’s there to move the engine down the track—not to toot the whistle. Too many people look at the power of the Holy Spirit as a whistle-tooter, as an end in itself—but the Lord says, “You shall receive power when the Holy Ghost comes upon you to be My witnesses” (Acts 1:8). Thus, when people ask why we don’t see more signs and wonders today, I say, “Go to Honduras. Go to Mexico. Go to Russia. Start evangelizing and watch and see what the Lord will do in you and the miracles that will flow through you.” But even if you never see an external sign, wonder, or miracle, you’re in good company. Jesus said of all of the men who had lived, John the Baptist was the greatest of them all. No man was greater—not Elijah who called down fire from heaven, not Elisha who raised the dead, not Moses who parted the Red Sea. Jesus said, “Among them that are born of women there hath not risen a greater than John the Baptist” (Matthew 11:11). And yet John did no miracle (John 10:41). So if you’ve never performed a miracle or even seen a miracle, take heart. You’re in good company. John did no miracle but “all things John spoke of this Man were true” (see John 10:41). What Man? Jesus Christ. Talking about Jesus is something I can do—and so can you. Yes, I would love to have the powerful, miraculous ministry of Paul. But in the meantime, I’ll try to walk in the footsteps of John the Baptist, pointing others to the Lamb of God." (Courson, J: Jon Courson's Application Commentary: NT. Nelson. 2004 or Logos)  (Bolding added)

God-centered evangelism must be carried out "in the power of the Spirit of God." God’s work must be done God’s way in God’s power.

Not by might, nor by power, but by My Spirit, saith the LORD of hosts" (Zech 4:6)

SO THAT FROM JERUSALEM AND ROUND ABOUT AS FAR AS ILLYRICUM I HAVE FULLY PREACHED THE GOSPEL OF CHRIST: Hoste me apo Ierousalem kai kuklo mechri tou Illurikou peplerokenai (RAN) to euaggelion tou Christou: (Romans 15:24; Acts 9:28,29; 13:4,5,14,51; 14:6,20,25; 16:6-12; 17:10,15; Acts 18:1,19; 19:1; 20:2,6 ) (Romans 1:14-16; Acts 20:20; Colossians 1:25; 2 Timothy 4:17)

From Jerusalem - Barnes notes that...

Jerusalem, was a centre of his work; the centre of all religious operations and preaching under the gospel. This was not the place where Paul began to preach, (Gal 1:17,18 "nor did I go up to Jerusalem to those who were apostles before me; but I went away to Arabia, and returned once more to Damascus. Then three years later I went up to Jerusalem to become acquainted with Cephas, and stayed with him fifteen days) but it was the place where the gospel was first preached, and the apostles began to reckon their success from that as a point. Compare (Lu 24:49 "And behold, I am sending forth the promise of My Father upon you; but you are to stay in the city until you are clothed with power from on high."). (Albert Barnes. Barnes NT Commentary)

Fully preached the Gospel of Christ - It was the Gospel and not the signs and wonders that saved the Gentiles and brought them to the obedience of faith.

Newell comments on...

What a marvelous, absolutely tireless love-laborer was this man Paul. Illyricum was the next province to Italy. Between Jerusalem and Illyricum lay the province of Syria, with its capital at Damascus, but its spiritual capital Antioch; and next to it Cilicia, with its great center Tarsus, Paul's own home, whither he had been sent by the brethren away from Jerusalem persecution (Acts 9:30) ; and whence Barnabas brought him to the work at Antioch (Acts 11:25,26) ; next province Pamphylia with Perga and Attalia; and above that Pisidia, centered at another Antioch; then Lycaonia, and above that the great and difficult Galatia with the churches Paul founded there; next proconsular Asia, centered at Ephesus, of course, and the mighty work there and the "fighting with beasts"; then at Troas across the Aegean came the call from Macedonia, and its cities Philippi, Berea and Thessalonica, the saints of which lay so close to the apostle's heart; then Achaia, centered at Corinth, whence he wrote this present letter to the Romans-vast city, vast wickedness, but much people for the Lord. And so we arrive at Illyricum. And through all these regions just traced, Paul has fulfilled the gospel of Christ; insomuch that verse 23 informs us that he had no more any place in these regions. (Romans Verse by Verse)

John Piper observes that...

Paul's missionary strategy was to preach where nobody has preached before. This is what we mean by Frontier Missions. Paul had a passion to go where there were no established churches—that meant Spain. What is amazing in these verses is that Paul can say he has "fulfilled" the gospel from Jerusalem in southern Palestine to Illyricum northwest of Greece! To understand this is to understand the meaning of Frontier Missions. Frontier Missions is very different from domestic evangelism. There were thousands of people yet to be converted from Jerusalem to Illyricum. But the task of Frontier Missions was finished. Paul's job of "planting" was done and would now be followed by someone else's "watering" (1 Corinthians 3:6) () (Desiring God) (bolding added)

Round about (2945) (kuklothen from kúklos = a circle + "-then"= from or at a place) literally means from the circle and so all around or round about. That is, taking Jerusalem as a centre, he had fully preached round that centre until you come to Illyricum. Don't miss what Paul is saying...you may need to look at a map to fully grasp the breath of his ministry (in the map above it would be from the bottom right (roughly the location of Jerusalem) to the upper left (Illyricum). I don't know about you, but I haven't even fully proclaimed the gospel to my cul-de-sac neighbors!

Illyricum is the area on the eastern shore of the Adriatic, extending from NE Italy to Macedonia (the former nation of Yugoslavia). This of course implies that this would have most likely been during or after his 3rd missionary journey.

From Jerusalem to Illyricum (region of former Yugoslavia) was a span of about 1,400 miles. Paul was clearly a man on mission! Although Acts does not record Paul visiting Illyricum, he may have visited during one of his stays in Macedonia.

Fully (4137) (pleroo) means first to fill up and here mean to fulfill, to complete, to carry out to the full (eg Lu 9:31 at the transfiguration, Moses and Elijah were "speaking of [Jesus'] departure which He was about to accomplish [pleroo] at Jerusalem"). In the present context pleroo conveys the idea of faithfully executed, carried out to the full or of one's commission fulfilled. Think of pleroo as picturing Paul so thoroughly preaching the gospel that it is diffused abroad and "fills up" all that region with the gospel. And his use of the perfect tense pictures the lasting impact of this filling up with the gospel preaching.

Paul makes a similar statement in Colossians writing...

Of this church I was made a minister according to the stewardship from God bestowed on me for your benefit, that I might fully carry out (pleroo) the preaching of the word of God (see note Colossians 1:25)

Pleroo is also used of John the Baptist who "fulfilled his course (of life)" (Acts 13:25). He completed His God-given assignment and so too did Paul fulfill his gospel assignment. How about you beloved? Are you fulfilling your God given assignment, the stewardship He has given you?

Guzik offers an interesting thought...

We sense that Paul would consider “bare” preaching, without the active and sometimes miraculous work of the Holy Spirit evident, to be less than fully preaching the gospel. (The Enduring Word Commentary Series)

In his last written words Paul reminded his faithful disciple Timothy that in spite of all the difficulties (including people deserting him and no one supporting him)...

the Lord stood with me, and strengthened me, in order that through me the proclamation might be fully accomplished, and that all the Gentiles might hear; and I was delivered out of the lion's mouth. (see note 2 Timothy 4:17)

To the very end of his earthly existence, Paul had faithfully diffused the knowledge of the gospel throughout that immense expanse that stretched about 1,400 miles from Jerusalem to the Roman province of Illyricum! Father, would you enable each of us to be found so faithful to our calling. Amen.

The Gospel (2098) (euaggelion) (Click word study of euaggelion) was originally a reward for good news, later becoming good news.

The word preached is added in this verse by the translators. The Greek literally reads "I have filled full the gospel" and could refer to preaching the full gospel message (cf. Acts 20:27) or to preaching throughout the full geographical area in which he was called to minister. Both meanings certainly describe Paul’s ministry, but the context (which is "king" and which facilitates accurate interpretation) seems to indicate that Paul was affirming his faithful and full ministry in every place to which the Lord sent him. In other words although not every individual person in those areas had heard the gospel from Paul, he clearly believed that he had fulfilled his work there and it was time to move on to other places.

Hodge writes that...

AND THUS I ASPIRED TO PREACH THE GOSPEL: houtos de philotimoumenon (PMPMSA) euaggelizesthai (PMN): (2 Corinthians 10:14-16