There are numerous sources, beginning in the first century, that have information about Jesus of Nazareth. There is a general consensus that there was a historical Jesus of Nazareth who lived in first-century AD Roman Judea and there are numerous portraits on who he was."He certainly existed, as virtually every competent scholar of antiquity, Christian or non-Christian, agrees, based on certain and clear evidence." B. Ehrman, 2011 Forged : writing in the name of God . p. 256-257 The only two events subject to "almost universal assent" are that Jesus was baptized by John the Baptist and was crucified by the order of the Roman Prefect Pontius Pilate. States that baptism and crucifixion are "two facts in the life of Jesus command almost universal assent".

To establish the existence of a person without any assumptions, one source from one author (either a supporter or opponent) is needed; for Jesus there are at least 12 independent sources from five authors from supporters and two independent sources from two authors from non-supporters, within a century of the crucifixion. Since historical sources on other named individuals from first century Galilee were written by either supporters or enemies, these sources on Jesus cannot be dismissed, and the existence of at least 14 sources from at least seven authors means there is much more evidence available for Jesus than for any other notable person from 1st century Galilee. Some scholars estimate that there are about 30 independent sources written by 25 authors who attest to Jesus overall. It is notable that some independent sources did not survive, but are broadly referenced directly in the surviving sources themselves (e.g. Luke) or inferred from modern source analysis.

The letters of Paul are the earliest surviving sources referencing Jesus, and Paul documents personally knowing and interacting with eyewitnesses such as Jesus' own brother James and some of Jesus' closest disciples (e.g. Peter and John) around 36 AD, within a few years of the crucifixion (30 or 33 AD). Paul was a contemporary of Jesus and throughout his letters, a fairly full outline of the life of Jesus can be found.Jesus and the Gospels: An Introduction and Survey by Craig L. Blomberg 2009 Baker Academic pp. 441-442Eddy, Paul; Boyd, Gregory (2007). The Jesus Legend: A Case for the Historical Reliability of the Synoptic Jesus Tradition. pp. 202, 209-228

The Gospels are commonly seen as literature that is based on oral traditions, Christian preaching, and Old Testament exegesis with the consensus being that they are a variation of Greco-Roman biography; similar to other ancient works such as Xenophon's Memoirs of Socrates.

The non-Christian sources that are used to study and establish the historicity of Jesus are Josephus (a Jewish historian and commander in Galilee) and Tacitus (a Roman historian and Senator). These sources are compared to Christian sources such as the Pauline Epistles and the Synoptic Gospels. Such sources are usually independent of each other (as, in general, Jewish sources do not draw upon Roman sources), and similarities and differences between them are used in the authentication process.

From just Paul, Josephus, and Tacitus alone, the existence of Jesus along with the general time and place of his activity can be confirmed.

Non-Christian sources

Key sources

Josephus

The writings of the 1st century Romano-Jewish historian Flavius Josephus include references to Jesus and the origins of Christianity.Feldman, Louis H.; Hata, Gōhei, eds. (1987). Josephus, Judaism and Christianity BRILL. . pp. 54–57Maier, Paul L. (December 1995). Josephus, the essential works: a condensation of Jewish antiquities and The Jewish war. Kregel Academic. pp. 284–285 Josephus was a Jewish historian and commander in Galilee, where Jesus ministered, who trained 100,000 men in the region and even stationed in Sepphoris for a time, which was 3 miles away from Jesus's hometown of Nazareth; thus, he dwelled with inhabitants who would have known Jesus and knew participants in the trials of Jesus and his brother James such as the Sanhedrin and Ananus II. Josephus' Antiquities of the Jews, written around 93–94 AD, includes two references to Jesus in Books 18 and 20.Maier, Paul L. (December 1995). Josephus, the essential works: a condensation of Jewish antiquities and The Jewish war. Kregel Academic. p. 12 Both the Testimonium Flavianum in Book 18 and the James passage in Book 20 are used by scholars to support the existence of Jesus.Kostenberger, Andreas J.; Kellum, L. Scott; Quarles, Charles L. (2009). The Cradle, the Cross, and the Crown: An Introduction to the New Testament pp. 104–105

The Testimonium Flavianum (meaning the testimony of Flavius [Josephus]) is the name given to the passage found in Book 18, Chapter 3, 3 of the Antiquities in which Josephus describes the condemnation and crucifixion of Jesus at the hands of the Roman authorities.Flavius Josephus; Whiston, William; Maier, Paul L. (May 1999). The New Complete Works of Josephus. Kregel Academic. p. 662Schreckenberg, Heinz; Schubert, Kurt (1992a). Jewish Traditions in Early Christian Literature. 2. pp. 38–41 Since the late 20th century, the general consensus has held that the Testimonium is at least partially authentic in that an authentic nucleus referencing the life of Jesus was original to the Greek text.Evans, Craig A. (2001). Jesus and His Contemporaries: Comparative Studies p. 316Wansbrough, Henry (2004). Jesus and the oral Gospel tradition. p. 185 Although the exact nature and extent of the Christian redaction remains unclear,Wilhelm Schneemelcher, Robert McLachlan Wilson, New Testament Apocrypha: Gospels and Related Writings, p. 490 (James Clarke & Co. Ltd, 2003). there is broad consensus as to what the original text of the Testimonium by Josephus would have looked like. According to G. J. Goldberg, the Testimonium may be a paraphrase of Luke's Emmaus narrative (Luke 24:18–24) thus rendering Christian interpolation unlikely and validating an earlier trustworthy source attesting to Jesus existing. A statistical analysis of the vocabulary and frequency of terms from all the works of Josephus rendered the passage as Josephan and observed that most ancient Christian sources interpreted the passage as a negative or neutral portrayal of Jesus, indicating it is authentic. The passage is found in all extant manuscripts.

Modern scholarship has almost universally acknowledged the authenticity of the reference in Book 20, Chapter 9, 1 of the Antiquities to "the brother of Jesus, who was called Christ, whose name was James",Louis Feldman ( pp. 55–57) states that the authenticity of the Josephus passage on James has been "almost universally acknowledged". and considers it as having the highest level of authenticity among the references of Josephus to Christianity.Van Voorst, Robert E. (2000). Jesus Outside the New Testament: An Introduction to the Ancient Evidence. Wm. B. Eerdmans Publishing Co.. p. 83Richard Bauckham "For What Offense Was James Put to Death?" in James the Just and Christian origins by Bruce Chilton, Craig A. Evans 1999 pp. 199–203Painter, John (2005). Just James: The Brother of Jesus in History and Tradition. pp. 134–141Sample quotes from previous references: Van Voorst ( p. 83) states that the overwhelming majority of scholars consider both the reference to "the brother of Jesus called Christ" and the entire passage that includes it as authentic." Bauckham ( pp. 199–203) states: "the vast majority have considered it to be authentic". Meir ( pp. 108–109) agrees with Feldman that few have questioned the authenticity of the James passage. Setzer ( pp. 108–109) also states that few have questioned its authenticity.

Most scholars accept the authenticity of the James passage since the account of James differs from later accounts of James by Christians. Very few have ever advocated for inauthenticity and their claims have been addressed.Eddy, Paul; Boyd, Gregory (2007). The Jesus Legend: A Case for the Historical Reliability of the Synoptic Jesus Tradition. pp. 188-190 The passage deals with the death of "James the brother of Jesus" in Jerusalem. Whereas the works of Josephus refer to at least twenty different people with the name Jesus, this passage specifies that this Jesus was the one "who was called Christ".Eddy, Paul; Boyd, Gregory (2007). The Jesus Legend: A Case for the Historical Reliability of the Synoptic Jesus Tradition. pp. 189–190Painter, John (2005). Just James: The Brother of Jesus in History and Tradition. p. 137 Louis Feldman states that this passage, above others, indicates that Josephus did say something about Jesus.Feldman, Louis H.; Hata, Gōhei. Josephus, Judaism and Christianity. Brill. . p. 56

The references found in Antiquities have no parallel texts in the other work by Josephus such as the Jewish War, written twenty years earlier, but some scholars have provided explanations for their absence, such as that the Antiquities covers a longer time period and that during the twenty-year gap between the writing of the Jewish Wars () and Antiquities (after 90 AD) Christians had become more important in Rome and were hence given attention in the Antiquities.Feldman, Louis H. (1984). "Flavius Josephus Revisited: The Man, his Writings and his Significance". In Temporini, Hildegard; Haase, Wolfgang. Aufstieg und Niedergang der römischen Welt, Part 2. pp. 763–771. p. 826

A number of variations exist between the statements by Josephus regarding the deaths of James and the New Testament accounts.Painter, John (2005). Just James: The Brother of Jesus in History and Tradition. pp. 143–145 Scholars generally view these variations as indications that the Josephus passages are not interpolations, because a Christian interpolator would more likely have made them correspond to the Christian traditions. Robert Eisenman provides numerous early Christian sources that confirm the Josephus testament, that James was the brother of Jesus.Eisenman, Robert (2002), "James the Brother of Jesus: the key to unlocking the secrets of Early Christianity and the Dead Sea Scrolls" (Watkins)

Tacitus

The Roman historian and senator Tacitus referred to Jesus, his execution by Pontius Pilate and the existence of early Christians in Rome in his final work, Annals (), book 15, chapter 44.P. E. Easterling, E. J. Kenney (general editors), The Cambridge History of Latin Literature, p. 892 (Cambridge University Press, 1982, reprinted 1996). A political history of early Christianity by Allen Brent 2009 pp. 32–34Robert Van Voorst, Jesus Outside the New Testament: An Introduction to the Ancient Evidence, Wm. B. Eerdmans, 2000. pp. 39–53 The relevant passage reads: "called Christians by the populace. Christus, from whom the name had its origin, suffered the extreme penalty during the reign of Tiberius at the hands of one of our procurators, Pontius Pilatus."