Some hold that singing in the Spirit is identified with singing in tongues in 1 Corinthians 14:13–19[50],[51] which they hold to be "spiritual or spirited singing", as opposed to "communicative or impactive singing" which Paul refers to as "singing with the understanding".[52] Sign for unbelievers (1 Cor 14:22). Some assume that tongues are "a sign for unbelievers that they might believe",[53] and so advocate it as a means of evangelism. Others point out that Paul quotes Isaiah to show that "when God speaks to people in language they cannot understand, it is quite evidently a sign of God's judgment"; so if unbelievers are baffled by a church service they cannot understand because tongues are spoken without being interpreted, that is a "sign of God's attitude", "a sign of judgment".[54] Some identify the tongues in Acts 2 as the primary example of tongues as signs for unbelievers Comprehension.