The office of "bishop" was non-existent in the first century: number of sources demonstrate this fact. There were EPISKOPOI and DIAKONOI, but no "bishops" in the technical sense of the word. Francis Beare writes concerning Phil 1:1:
"The two words translated bishops and deacons have been much debated. In the second century they became specialized in ecclesiastical usage; the bishop as the head of the local Christian community, the deacons as his assistants in whatever duties he might assign them."
Beare then adds: "Negatively, it may be said that the use of the plurals [in Phil 1:1] rules out any possibility that the Philippian church is governed by a monarchical bishop."
After citing Polycarp and other sources, Beare concludes: "This passing reference [to EPISKOPOI and DIAKONOI in Phil 1:1] does not provide us with any crumb of information about the status or function of EPISKOPOI and DIAKONOI at Philippi; and we are not entitled to read into them in this context the significance which belongs to them in later Catholic usage" (Francis Beare, Epistle to the Philippians, 1959, pp 49-50).
So while the Primitive Congregation used EPISKOPOI and DIAKONOI, it does not follow that these "offices" were hierarchically arranged or that these men were leaders of the Church. The EPISKOPOI and DIAKONOI were "individuals designated for special service within the Church and perhaps subject to the Church" (Gerald Hawthorne, Philippians, Word Series, page 8).
Heinrich Meyer also reasons: "We may add that placing of the officials after the church generally, which is not logically requisite, and the mere subjoining of them by SUN, are characteristic of the relation between the two [the overseers, assistants and the flock], which had not yet undergone hierarchical dislocation" (Meyer, Philippians and
Colossians, page 14).
Jesus Christ issued this command: "Neither be called 'leaders,' [KAQHGHTAI] for your Leader [KAQHGHTHS] is one, the Christ [hO XRISTOS]" (Mt 23:10 NWT).
Admittedly, the term translated "Leader" can evidently mean either "leader, master, guide, teacher or professor." Certain scholars favor the sense "teachers" in this passage, but I think that "leader" is just as likely in view of Mt 23:6-8.
The Geneva Bible of 1599 has: "Neither be ye called masters: for one is your Master, [even] Christ."
"Neither be ye called masters: for one is your master,[even] the Christ" (ASV).
"nor may ye be called directors, for one is your director -- the Christ" (YLT).
One could argue that Jesus is saying that his followers should not be called "leaders" or "teachers" (i.e., they should not be given these titles). But I think such an argument, if valid, simply makes the important point.
Ellicott's Commentary: "Neither be ye called masters.—The word is not the same as in Matthew 23:8, and signifies 'guide,' or 'leader;' the 'director' of conscience rather than the teacher. (Comp. Romans 2:19.)"