Paul uses the term αποστολος (“one who is sent”; cf. John 13:16) in three basic senses: (1) in a general, non-technical sense, of an emissary, delegate, representative, or messenger commissioned by people for a specific task (2 Cor 8:23, of Titus’ two companions; Phil. 2:25, of Epaphroditus); (2) in a semi-technical sense, of a Christian with a particular, permanent commission from Christ or the local church (Rom 16:7, of Andronicus and Junia[s]; 1 Cor 9:5-6, of Barnabas, by implication [cf. Acts 14:4, 14]; 1 Cor 15:7 and Gal. 1:19, of James, the brother of Jesus; and possibly 1 Cor 4:9, of Apollos, by implication from 1 Cor 4:6; and 1 Thess 2:7, of Silas); (3) in a technical sense, of the Twelve (1 Cor 15:5, 7; Gal 1:17; cf. Luke 6:13) and of himself (1 Cor 9:1; 15:9) as commissioned directly by Christ for permanent and distinctive leadership in the universal church. With regard to apostolic status, Paul recognised no distinction between himself and the Twelve (1 Cor 9:1, 5; 15:8-10; 2 Cor 11:5; 12:11; Gal 2:6). For Paul’s view of the qualifications for apostleship (in sense ), see [2 Cor] 12:12.
These distinctions are ubiquitous among scholars of early Christianity and yet they have a tradition of being asserted and not demonstrated. But I wish to suggest that the distinctions between non-technical, semi-technical and technical senses of the word “apostle” are in fact dubious and an unnecessary imposition on the texts of the New Testament. The prevailing assumption must be challenged and an alternative model should be offered. The alternative that I propose is simply that we may infer a historical distinction between apostles who were disciples/witnesses of Jesus and those who were not, but that this did not amount to a theological difference in leadership or authority that the apostles had. The New Testament demonstrates a wide understanding of apostolic ministry and apostolic succession that is not limited to the Twelve or to Paul. There are a variety of apostles engaged in various apostolic ministries. The burden of this claim is the purpose of my current research. What do you think?
 M. J. Harris, The Second Epistle to the Corinthians (Eerdmans, 2005), pg. 128