Paul begins chapter 2 with four conditions that every believer has already met. They are conditions that already exist and there is no uncertainty with them with respect to a Christian. We all have, “encouragement in 
Christ, comfort from love, participation in the Spirit as well as affection and sympathy.” These conditions of the believer, according to Paul, become the basis for Christian unity. Paul pleads with his readers on the basis of these four certain conditions, in Philippians 2:2, to “complete my joy by being of the same mind, having the same love, being in full accord and of one mind.”
Notice that the exhortation begins with “the same mind” and ends with “of one mind.” He’s going to go on and explain what the “mind of Christ” is all about and how we should have the same thought. I think this expresses the idea of a single goal, or a unified purpose. It surely doesn’t mean we shouldn’t have different opinions on issues. We certainly do. It doesn’t mean that we will always think the same thoughts from a human point of view. That would be impossible and make most of us unnecessary! It also does not mean that everyone must interpret everything the same way. But it does mean that we are to think like Christ thinks. In 1 Corinthians 2:16, Paul actually says point blank, “We have the mind of Christ.”
Christ’s one thought, his total purpose was the redemption of the world. He “set his jaw” and would not be moved from that agenda. Before he left he also passed his mission and agenda off to us. He said, “Make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit and teach them to observe all that I’ve commanded you. And I will be with you always, even to the end of the age.” So, what is the unified goal? I like the way, Kent Hughes explains it. He says that the unified goal is “The gospel! Paul mentioned the gospel five times in the first chapter, and in the fifth mention (verse 27) he declared, ‘Only let your manner of life be worthy of the gospel,’ which is the commanding theme all the way to 2:18. So the call here in 2:2 to be ‘of the same mind, having the same love, being in full accord and of one mind’ is a plea that the Philippians be ‘gospel oriented as they relate to and care for one another.’”