Commentaries:
Simplicity means single, without ulterior motive, pure, sincere, and unambiguous. Vincent's Word Studies (vol. 3, p. 346), defines it as "single-hearted loyalty." It is the opposite of deceit, guile, error, and wandering.
Some things in God's Word are difficult to understand (II Peter 3:16), but the Bible nowhere tries to produce doubt, confusion, or division by any means (I Timothy 6:3-5; II Timothy 2:14). Even Balaam knew that "God is not a man, that He should lie" (Numbers 23:19)! Jesus says, "[God's] word is truth" (John 17:17). The doctrines of God follow a logical and true sequence, locking together like a picture puzzle to comprise the true gospel.
John W. Ritenbaugh
Damnable Heresies
Paul had to deal with the Corinthian congregation because they had fallen under the sway of false apostles (see II Corinthians 11:13). These false ministers had convinced many of the brethren that they knew more and better than the apostle through whom they had heard, believed, learned, and been converted to the gospel. They were in the process of throwing aside what they had learned from Paul in favor of what they were hearing from these new "apostles."
John W. Ritenbaugh
Damnable Heresies