Revelation is given in creation and in history. In Biblical history there are two pivotal events - Exodus and Jesus Christ. Thus we have three important moments of revelation - creation, liberation from Egypt and the event of Jesus Christ. Bible is the story of human faith and faithlessness as well as God's dealings with these.
Old Testament (OT):
The word of God (creative and revelatory) addressed to people through varied ways; demanded and active response in faith, hope and love. All those responded in faith had the experience of the divine in their lives and expressed their experiences in symbols, myths and in other celebrations to their successive generations. Their experience of Exodus and Exile, the covenantal relationships, etc., held the chosen people together and their foundational experience assumed the form of tradition and was handed on orally to the next generation.
Gospels are not eye-witness reports; not apostolic memories either; not biographies but proclamation of the risen Jesus; the person and message of Jesus.
Gospels are faith-documents, records of faith experiences written to provoke this same experience in others; they are not history but history interpreted through faith.
The starting point of the gospel tradition is the historical Jesus of Nazareth whose words and works heard and seen by the disciples. The gospels are anecdotal rather than biographical. We find here stories, teaching and sayings of Jesus clubbed together – each unit independent but intrinsically connected to the whole by words like 'and' (Mk) 'then' (Mt). Place and time indications are frequent, vague and at times conflicting e.g. For Mt. the sermon is on the mount but for Lk it is on the plain (Lk.6: 17ff).
Studies about Jesus, his teachings and his activities were going around in different communities. The resurrection and Pentecost transformed the whole experience and so we can say that the post Easter memory of Jesus was a transformed memory.
The Jesus tradition, was orally handed down in strictly functional situations; teaching, preaching, liturgical worship and shepherding. Gospel traditions were formulated in the language of O.T. memorization, didacting, and poetic devices e.g. picturesque and pointed formulations, alliterations, rhythm phrases.
The founding members of oral traditions were either disappearing or killed or exiled or died. Nero's persecution in 64 A.D. brought the Christians together. Missionary activities roped in many converts and they demanded authentic documents. Destruction of Jerusalem in 70 A.D. left the Christians cut off from the roots and Christians did not want its origin mixed up with other legends. All these factors led to the writing of the gospels.
Stories and sayings of Jesus that were in functional forms, were gathered by evangelists and skilfully compiled, each one selecting his own materials and arranging them according to their community's needs and point of emphasis. Each one touches the tradition, interprets its edits and compiles it reflecting a particular point of view. Each has a particular understanding of Jesus, own theology. Hence the difference in interpretations, e.g. the parable of the lost sheep (Lk. 15:1-7 cf Mt. 1:10-14.) In Lk. it is addressed to the Pharisees who objected Jesus' fellowship with sinners. In Mt. the context is exhortation to the disciples as leaders of the church.
From oral traditions we reach a stage of earliest written documents. Casual reading of Mk, Mt, and Lk reveal a similarity in outline, form and content. Mt. and Lk. have in common which are not found in Mk. and also Mt. and Lk. have something peculiar to each other. Johannes Waris in 1881 called Mt, and Lk. Quelle, meaning 'source', in German, which is not in Mk. Q, has reference to places and things (countryside, grass, flowers, reeds, weeds) and also reference to the person of Jesus. Mark has used 'Q' materials very little (40 verses).
The synoptic problem: The gospels are not written by eye witness of Jesus’ ministry. They are written in the periods between 40 - 100 AD. Now the three gospels of Mt, Mk and Lk. stand together in many ways: similar outline of work, content arrangement and style. But there is also difference in plan, purpose and specific features. e.g. Mk. Gospel of 'sacred epiphanies,' proclaiming the words and works of Jesus as hidden manifestation of the Son of God. In Mt. we see Ecclesial gospel; church as the true Israel. In Lk. theology of salvation history and ministry of Jesus in the time of salvation it is the middle period between OT preparation and the Church's time of mission. The synoptic problems seek to find out why these three are much alike and why do they differ in many ways.
Mark's gospel was considered to have been written first because of the following reasons:
a) Almost the whole of Mk's gospel is found in Mt. and Lk.
b) Common order of events: Mt. and Lk. follow Mk.'s order.
c) Use of language: Mt and Lk. never agree but Mt and Mk; Lk. and Mk. agree.
d) Mk is the shortest. Mt. and Lk. expand pericope.
e) Mk is simple, less systematic, less coherent, less theological interpretation and more primitive in origin.