This study combines traditional historical-critical methods with the sociological theories of Max Weber and Pierre Bourdieu in order to discuss how Peter's authority is portrayed and used to create legitimacy in Christian texts from the first three centuries. The New Testament texts that mention Peter are discussed together with other early Christian writings that in one way or another relate to Peter as an authoritative figure. Peter emerges as a central figure in the diverse early Christian movement and is used to a high degree to discuss theological legitimacy. The main divide is between those who argue that legitimate theology should have a conservative point of departure based on traditional material handed down from the earthly Jesus and an apostolic succession based on interpersonal relations and those who argue in favour of a more progressive point of departure which places more emphasis on contemporary charismatic experiences. Both these perspectives are used by groups of various theological persuasion in order to argue their own position. Peter is sometimes used to legitimise a theological position with reference to Peter's relationship to the earthly Jesus and sometimes to discredit traditions concerning the earthly Jesus by pointing out that Peter did not understand his true message. Peter is used as both positive and negative example for both these ways of creating legitimacy.