The Corinthian church had an immaturity problem. They argued over petty things. Paul is calling them to grow up and be mature. The mark of maturity is a Christian who is mature in their thinking and infants in evil. They are looking to advance the kingdom of God and not gossip about someone in the church. 
1 Corinthians 14:20-25
Brothers, do not be children in your thinking. Be infants in evil, but in your thinking be mature. In the Law it is written, “By people of strange tongues and by the lips of foreigners will I speak to this people, and even then they will not listen to me, says the Lord.” Thus tongues are a sign not for believers but for unbelievers, while prophecy is a sign not for unbelievers but for believers. If, therefore, the whole church comes together and all speak in tongues, and outsiders or unbelievers enter, will they not say that you are out of your minds? But if all prophesy, and an unbeliever or outsider enters, he is convicted by all, he is called to account by all, the secrets of his heart are disclosed, and so, falling on his face, he will worship God and declare that God is really among you.
Be Focused
Confusion is one of Satan’s tools used to diminish the influence of the church. Tongues confuse unbelievers but prophecy convicts. If everyone in the church is speaking in tongues unbelievers are going think we are mad. The Corinthians were extremely immature. They wanted the attention to be on them when they used their gifts. You had people in their selfishness speaking tongues all at the same time. So Paul tells them “Be infants in evil, but in your thinking be mature.” This is easy to understand. We don’t want to be experienced in our evil but in our thinking.
Reduce the Confusion
To fully understand this passage we have to know that Paul is quoting Isaiah 28. In that chapter, God tells Israel that judgment will come through foreign tongues. This came true when the Assyrians invaded and spoke in a language the Israelites could understand which produced fear in the people. With that in mind, Paul is using it as a way to teach what happens to an unbeliever when they come to the church, and everyone is speaking in tongues. They can’t understand. If people prophesy, unbelievers, would not only understand but be convicted of their sin and turn to worship God. It’s important that we don’t produce more confusion in the church than necessary. When we teach the Bible, we don’t water it down, but we strive to make it understandable. It is also important that the believers act maturely as an example the unbelievers can model their lives after.