Since the Enlightenment, scholars have tried to distinguish the historical Jesus from the figure worshiped in Christianity, although Albert Schweizer commented that scholars who set out on a "Quest for the Historical Jesus" tend to discover in him a reflection of their own views. Some scholars focused doubt on the biblical accounts of miracles. Others saw Jesus as a moral teacher whose views are best represented by the Sermon on the Mount. In recent decades, the name "Jesus Studies" has come to describe historical (as opposed to theological) approaches to the study of Jesus.
The most important sources of information, the four canonical gospels, have several shortcomings as historical sources:
- Their authors are not known (despite the titles assigned to them by church tradition); thus we have no way of knowing how they acquired their information.
- Their composition appears to involve multiple authors and an active editorial process. For example, the synoptic gospels share much material, albeit rearranged.
- They appear to have been written at least a generation after Jesus's death. (Mark, the oldest, is usually dated within a few years of AD 70.)
- No first-century manuscripts survive.
- They report many supernatural events, which many historians consider to be prima facia evidence of their unreliability.
- Their authors were committed believers, not disinterested observers.
- Some details (such as the Census of Quirinius mentioned in Luke 2:1) conflict with what we know of the history of the time.
- They show signs of adapting their stories to make theological points. For example, Matthew (21:1 ff) describes Jesus as entering Jerusalem while seated on not one but two animals, a donkey and a colt--this might be a misunderstanding of Zachariah 9:9, (which Matthew quotes).
- Some stories appear to have been inspired by Old Testament prototypes. For example, Christ's miracles in Matthew 8 and 9 parallel the miracles of Elisha in 2 Kings 4 - 6.
Several ancient authors who were not Christians mention Jesus. They are: Flavius Josephus, Pliny the Younger, Tacitus, and Suetonius. With the possible exception of Josephus (and here the textual integrity is a concern), their information about Jesus probably relies on Christian sources.
Saint Paul apparently met some of Jesus's relatives and companions (although not Jesus himself, except through visions). Unfortunately, his epistles offer almost no biographical details. Donald Harmon Akenson suggests that the teachings of Paul--especially those which are also attested in the earlier strata of the gospels--are likely to incorporate genuine Jesus traditions.
Noncanonical Christian literature is voluminous but relatively late, with the following possible exceptions: the Gospel of Thomas, the Unknown Berlin Gospel, the Oxyrhynchus Gospels, the Egerton Gospel, the Fayyum Fragment, the Dialogue of the Saviour, the Gospel of the Ebionites, the Gospel of the Hebrews, and the Gospel of the Nazarenes. The earliest surviving fragments of these texts are dated later than the earliest surviving fragments of the canonical Gospels, but they are probably copies of manuscripts whose dates are unknown.
Many scholars point to a hypothetical, reconstructed text called "Q" (from the German Quelle, meaning "source") as a possible older text that might bridge the gap between the time of Jesus and the composition of the gospels. This hypothesis is based on the fact that the three synoptic gospels (Matthew, Mark, and Luke) share much material in common. In particular, both Matthew and Luke include almost all of Mark's material (and are both about twice as long as Mark), suggesting that Mark came first, and was incorporated into Matthew and Luke. However, Matthew and Luke also share other material not found in Mark, suggesting that they were also copying from another, no longer extant text. Thus "Q" is anything that is in Matthew and Luke, but not in Mark. This material consists largely of sayings of Jesus--exactly the sort of document one would expect to have been composed at an early date. (The Gospel of Thomas follows this pattern, being a collection of logoi.) The assumption is that Jesus lore would have circulated as oral tradition and collections of written logoi before its incorporation into the gospels.
Some scholars believe that different elements within Q were written at different times. If so, this would place the older elements closer to the time of Jesus. However, many either reject the two-source hypothesis (for example, the Augustinian hypothesis holds that Luke copied Matthew and Mark); consider Q to be later (John Spong explains its contents as midrash); or view Q as a non-Christian import (i.e. pre-existing logoi which were only later attributed to Jesus--this being the view of Earl Doherty).
Other theoretical documents include the Signs Gospel, which Rudolf Bultmann believed to have been a source for the Gospel of John; and the "Cross Gospel" which John Dominic Crossan identifies as the source of the noncanonical Gospel of Peter.
Degrees of Skepticism
Problems with sources have led a few scholars to suggest that the story of Jesus is a myth, like various other Near Eastern deities or demigods (e.g. Mithras, Apollo, Attis, Horus, Osiris-Dionysus) who experienced virgin birth and / or resurrection from the dead. One counter-argument is the criterion of embarrassment. This holds that a gospel detail which early Christians would have found embarrassing is more likely to be true. An example is Jesus's execution as a criminal, an element not included in any known Jewish traditions of the messiah. Were Jesus entirely fictional, his story may have ended differently. The more likely story is that gentile Christians concocted the Jewish mistreatment of Jesus to validate their antisemitism.
Jesus's baptism by John is another example. This would have been embarrassing to early Christians because of (a) the suggestion that Jesus had sins to be forgiven, and (b) the inferior role of Jesus viz. John. Matthew (3:13-15) even has John object to the arrangement, only to hear Jesus insist. All four gospels stress John's expectation of another greater than himself, as if this required emphasis. In this connection, the Mandaeans of southern Iraq are a gnostic sect which venerates John but not Jesus, whom they regard as a schismatic who abandoned the Baptist movement. Other details that arguably fit the criteria include Jesus's statement (Mark 10: 18, cf. Luke 18:19) "Why do you call me good? No one is good but God alone." However, the more likely explanation is that Christians were merely attempting to co-opt the popularity of the more famous John.
Another principle is that a claim is more likely to be true if it appears in several independent sources. The gospels may not qualify, as their textual history is bound together, and they were apparently selected for preservation by the same sect. Hence the importance of confirmation from other ancient sources; or failing that, of recovering source-texts and otherwise distinguishing between strata of texts otherwise thought to be unitary.
Jesus in Context
In 70 CE, the Temple of Jerusalem was destroyed. Before then, Judaism was a temple-centered religion--not so different, perhaps, from other Near Eastern temple cults. While many religious movements disagreed about the teachings of Judaism, all did so in the context of this temple-centered religion.
After 70 CE, instead of a "religion of the temple", one sect (which came to represent Judaism as a whole) become a "People of the Book," i.e., the Torah. Another sect recognized Jesus Christ, as the new center of their religion, abandoning a purely ethnic Jewish identity. The notorious "blood curses" from the gospels, and the Eighteen Benedictions (really curses) from the synagogue service, probably reflect mutual ill-will between the two emerging religions.
Much of the difficulty in uncovering who Jesus was centers around dating the sources that wrote about him. Many scholars argue that while Jesus is claimed to be crucified well before 70 CE, and at least most of the sources about him--except for Saint Paul, the Gospel of Mark, and possibly Q--were composed later, and reflect different contexts. Other scholars date the New Testament works closer to the time of Christ, placing the synoptic gospels in the 50's and 60's, while John may be places before or after 70 AD.
Aspects of Second Temple Judaism with which Jesus is commonly associated include:
- Apocalypse: A major category of Jewish thought and literature consisting of revelations delivered by angels or other spiritual beings, often through visions, and emphasized such themes as the resurrection of the dead; the Last Judgment, the geography of heaven and hell, and prophecy (either messianic / millennial, or catastrophist, and often symbolic). Pre-Christian examples would include Ethiopic Enoch, 4 Ezra, and the Book of Jubilees. The gospels sometimes resemble this genre (e.g. the Little Apocalypse, the phrase "Son of Man"). which became Early Christianity after the Great Commission spread his teachings to the Gentiles. Jesus is also connected to the apocalyptic tradition through John the Baptist, and his Pauline successors were apocalyptic. Bart Ehrman, noting that predictions of the end of the world have been made throughout Christian history, questions whether Jesus himself preached this. Paula Fredriksen observes that such notions were already "in the air," but speculates that Jesus's popularity, arrest and execution (in contrast to the leniency shown his followers) might be explained if he predicted that the end would come, not soon, but now. The theology of Matthew, Luke, and John may consist of a "realized eschatology" which would be a natural response to failed prophesy. A controversial point is whether Jesus claimed to be the Messiah. Mark suggests that this was kept secret (the "Messianic Secret"); some propose that the identification of Jesus with the messiah came after his death.
- Pharisaic Judaism: The Pharisaic movement--the predecessor of modern rabbinic Judaism --was a major faction in Second Temple Judaism. The only two ancient authors who claimed to be Pharisees (or former Pharisees) themselves were Josephus and Paul, both rather unique figures. The gospels portray Jesus as opposed to this movement (he calls them "hypocrites", "fools", "vipers", and "sons of your father the devil"), but some scholars suggest that Jesus was himself a Pharisee. The essence of Jesus's criticism seems to be that the Pharisees demanded stricter observance of halakhah than ordinary people, could follow. This is ironic in that Jesus's interpretations of Jewish law range from the strict (e.g., his prohibition of divorce, except on grounds of adultery) to the impractical (e.g., his equation of momentary lust with adultery). Christians who perhaps take Jesus too much at his word viz. the Pharisees might reflect that Jesus's "Greatest Commandment" quotes Leviticus and Deuteronomy by way of Hillel the Great (Matthew 22:34 ff; Luke 10:25 ff). Jacob Neusner contends that Jesus' teachings were closer to the House of Shammai than to the House of Hillel. 
- Social protest: Crucifixion was the prescribed form of execution for sedition against the Roman authorities. The gospels, written when Christians were seeking good relations with Rome, deny Jesus's guilt (although he is depicted as physically attacking money-changers). Apparently his claim was willfully misunderstood--he was "King of the Jews" only in a spiritual sense. A number of Jesus's near-contemporaries (e.g. Judas of Galilee) sought to oust Rome and reestablish Israel as an independent monarchy. The gospels and other sources mention a class of revolutionaries called Zealots (Jesus's disciples included "Simon the Zealot"--but also a Roman collaborator, "Matthew the tax-collector"); these may fit better the social category of banditry than that of nationalist resistance. Many scholars see political meaning in Jesus's naming of twelve disciples (corresponding to the Twelve Tribes of Israel). Some of the sayings attributed to Jesus (e.g. "blessed are the poor"; "the first shall be last") appear subversive of the established order. His concept of "The Kingdom of God" (or Heaven) is thought by some to have a political dimension involving debt forgiveness and the abandonment of burdensome purity requirements. In this sense, the "revolutionary" nature of Jesus's message would be his championing of the interests of the Palestinian peasant class.
- Palestinian folk religion: Reading the gospels, it is easy to imagine Jesus as delivering the equivalent of sermons--but less easy to imagine him as a kind of medium who allows himself to be possessed by an angel, or the Spirit of God (this is Stevan Davis's view), which then accomplishes teachings, healings and exorcisms through him. Second Temple Palestine saw several folk religious figures whose roles are as much magical as religious. Among them were Honi the Circle Drawer and Hanina ben Dosa, two characters from the Mishnah whose prayers could persuade God to allow healings, rainfall, or whatever else was requested. Marcus Borg proposes to call Jesus a "spirit person," among other roles, to underscore the degree to which he must have experienced the spirit as a living reality rather than mere theory.
- The Essene sect: The Essenes are mentioned by Josephus, Philo, and Pliny the Elder. Whether the Qumran community were Essenes is uncertain. The idea that Jesus was an Essene dates to 1717 (to Humphrey Prideaux), and seems to have been inspired by the observation that, of the three religious factions mentioned in Josephus, Jesus vilifies two (the Pharisees and Saducees), whereas the Essenes are not mentioned in the New Testament. Intriguing parallels between early Christianity and Josephus's Essenes include the practice of communism (especially communal meals) and their shared objection to taking oaths. 
- Cynic philosophy: Newcomers to Jesus Studies may be surprised at the suggestion that Jesus belonged to a Hellenistic gentile philosophical movement--especially one famed for such eccentric figures as Diogenes of Sinope. Yet several members of the Jesus Seminar, including John Dominic Crossan, Robert Funk and Burton Mack, have argued this. They point out that the Palestinian Jewish culture of Jesus's day was heavily Hellenized, and that the Cynics were a serious social movement that produced a wisdom literature analogous, they say, to Q1. Nevertheless, the identification of Jesus with Cynicism is a minority view.
The gospels agree on the names of Jesus's mother, Mary, and all but Mark name Joseph as his father. Joseph appears only in descriptions of Jesus' childhood, whereas Mary is present at the crucifixion, and this has led some Christians to speculate that Joseph died before then.
In the Gospel of John, Jesus entrusts the care of his mother to the "beloved disciple" (who traditionally is thought to mean John). If historical, suggesting that he had no surviving male relatives. However, Matthew 13:55-56 and Mark 6:3 (cf. Galatians 1: 19) name several "brothers" (adelphoi) and allude to sisters as well. Orthodox and Catholic Christians insist that a different family or affectionate relationship is meant, as they believe that Mary remained a lifelong virgin, with Jesus as her only child.
Josephus names Jesus's "brother," James (or Jacob) the Righteous (or Just, probably ha-Zaddik)as having headed the Jerusalem church after Jesus's death, and mentions other blood relatives of Jesus. James is believed by some to be interred in an ossuary that was brought into public attention by the Discovery Channel in 2002. The ensuing well publicized dispute over the provenance of the ossuary gained further attention in 2007 when the Discovery Channel aired a new documentary by Director James Cameron, called The Lost Tomb of Jesus, that asserts a link between this ossuary with others which are claimed to be those of the entire Holy Family.
The gospels do not say whether Jesus was married. Jewish tradition discourages celibacy, but there are exceptions for special situations such as war, and some Jewish groups (such as the Essenes) practiced it on this basis. Some modern scholars have speculated that Mary Magdalene was his wife. The Secret Gospel of Mark, rejected by many as a 20th century fraud, hints that Jesus practiced ritual homosexuality. Mormon tradition holds that Jesus was (and remains) plurally married, to Mary and Martha.
- The Gospel accounts show both John the Baptist and Jesus teaching repentance and the coming Kingdom of God. Some scholars have argued that Jesus was a failed apocalyptic prophet; see Schwietzer, Albert The Quest of the Historical Jesus: A Critical Study of its Progress from Reimarus to Wrede, pp 370–371, 402. Scribner (1968), ISBN 0-02-089240-3; Ehrman, Bart Apocalyptic Prophet of the New Millennium, Oxford University Press USA, 1999. ISBN 0-19-512474-X. Crossan, however, distinguishes between John's apocalyptic ministry and Jesus' ethical ministry. See Crossan, John Dominic, The Birth of Christianity: Discovering What Happened in the Years Immediately After the Execution of Jesus, pgs. 305-344. Harper Collins, 1998. ISBN 0-06-061659-8.
- This includes the belief that Jesus was the Messiah. Brown, Michael L. Answering Jewish Objections to Jesus: Messianic Prophecy Objections Baker Books, 2003. ISBN 0-8010-6423-6. Brown shows how the Christian concept of Messiah relates to ideas current in late Second Temple period Judaism. See also Klausner, Joseph, The Messianic Idea in Israel: From its Beginning to the Completion of the Mishnah, Macmillan 1955; Patai, Raphael, Messiah Texts, Wayne State University Press, 1989. ISBN 0-8143-1850-9; Crossan, John Dominic, The Birth of Christianity: Discovering What Happened in the Years Immediately After the Execution of Jesus, p 461. Harper Collins, 1998. ISBN 0-06-061659-8. Patai and Klausner state that one interpretation of the prophecies reveal either two Messiahs, Messiah ben Yosef (the dying Messiah) and Messiah ben David (the Davidic King), or one Messiah who comes twice. Crossan cites the Essene teachings about the twin Messiahs. Compare to the Christian doctrine of the Second Coming.
- Based on a comparison of the Gospels with the Talmud and other Jewish literature. Sanders, E. P. Jesus and Judaism, Fortress Press, 1987. ISBN 0-8006-2061-5; Maccoby, Hyam Jesus the Pharisee, Scm Press, 2003. ISBN 0-334-02914-7; Falk, Harvey Jesus the Pharisee: A New Look at the Jewishness of Jesus, Wipf & Stock Publishers (2003). ISBN 1-59244-313-3. See also Jesus the Pharisee, forthcoming from Hyam Maccoby.
- Jacob Neusner, A Rabbi Talks With Jesus, McGill-Queen's University Press, 2000. ISBN 0-7735-2046-5.
- Based on a comparison of the Gospels with the Dead Sea Scrolls, especially the Teacher of Righteousness and Pierced Messiah. Eisenman, Robert James the Brother of Jesus: The Key to Unlocking the Secrets of Early Christianity and the Dead Sea Scrolls, Penguin (Non-Classics), 1998. ISBN 0-14-025773-X; Stegemann, Hartmut The Library of Qumran: On the Essenes, Qumran, John the Baptist, and Jesus. Grand Rapids MI, 1998. See also Broshi, Magen, "What Jesus Learned from the Essenes," Biblical Archaeology Review, 30:1, pg. 32-37, 64. Magen notes similarities between Jesus' teachings on the virtue of poverty and divorce, and Essene teachings as related in Josephus' The Jewish Wars and in the Damascus Document of the Dead Sea Scrolls, respectively.