Paul has been chastizing and reproving the Corinthians throughout his letter to them. His primary criticism of the church there in Corinth is that they have created divisions amongst them. Whether the divisions would be because of who they follow, because of their pride, or because of sin – or even tolerance of sin – the overriding problem is that they are divided and continuing in their division.
Paul says, though, that God has given them a way to unify, that is unity through the Holy Spirit:
For we were all baptized by one Spirit so as to form one body—whether Jews or Gentiles, slave or free —and we were all given the one Spirit to drink.
1 Corinthians 12:13
Diversity can be a significant challenge. Different nations, different languages, and different backgrounds or cultures can cause significant difference. We experience this even in our little group, our little church here in Catania. But God made us to be unified. We are unified in Christ, through the giving of the Holy Spirit. There is one God and he gives himself to us through the Holy Spirit. The Spirit, God himself, lives inside of us and through him we are unified.
Paul told us what that looks like when we have the Holy Spirit and walk through our lives according to his leading. It looks like love, joy, peace, patience, kindness, goodness, faithfulness, and self-control. These are the qualities of character that we have through the Holy Spirit, and these are the qualities of character that will create unity, that will create oneness.
Paul spoke of us being like a body, the body of Christ. We are many parts, with different roles and different gifts, but one. We are animated by the same Spirit, given breath and life by him, yet though individual parts, made one in the body of Christ in unity. This is who we are called to be and as we walk by the Spirit of Christ, we will be made one in him.