Is Mark’s gospel based on eyewitness testimony. Richard Bauckham revisits, in Jesus and the Eyewitnesses the case for Peter as the main eye witness source.
I want to give you two of his reasons.
Inclusio of Eyewitness Testimony: The most authoritative eyewitnesses of the life of Jesus are those who were present from the beginning of his ministry (John the Baptist) until the resurrection. The gospels use a literary device called the inclusio of eyewitnesses, also used in two Greek biographies, by which the a character in the story is placed into the beginning and the end of the story, to show that he is one of the main sources of information. In Mark’s gospel Peter is mentioned in the early stages (Mark 1:16-18) and at the end (Mark 16:7).
Plural to Single Narrative Devise is predominantly found in Mark’s gospel. This device is illustrated in the following verses.
Mk 5:1-2 (NRSV) 1 They came to the other side of the sea, to the country of the Gerasenes. 2 And when he had stepped out of the boat, immediately a man out of the tombs with an unclean spirit met him.
Mark 8 22 They [Plural]came to Bethsaida. Some people brought a blind man to him[Singular] and begged him to touch him.
Mark 11:12 (NRSV) 12 On the following day, when they came from Bethany, he was hungry.
Mark 14:32 (NRSV)32 They went to a place called Gethsemane; and he said to his disciples, “Sit here while I pray.”
This occurs 21 times in Mark. However this seems to be unnatural in Greek as textual variants abound which put these verses back into singular/singular, also Matthew and Luke change a good number of these verse back into singular/singular. This seems to indicate that the account is based on eyewitness testiomony in which they would say, for Mark 8:22, we came to Bethsaida. .