“You therefore, beloved, since you know this beforehand, beware lest you also fall from your own steadfastness, being led away with the error of the wicked [unprincipled men]…”
lest you also fall
The idea of “fall” implies a point of instability. The word “fall” is a term of apostasy. The book of Acts uses “fall” as a nautical term for a ship out of control or drifting off course (Acts 27:17,26,29,32). The Word of God cannot “fall away” from the purpose God gave it (Romans 9:6). Some fall from grace (Galatians 5:4).
“You have become estranged from Christ, you who attempt to be justified by law; you have fallen from grace” (Galatians 5:4).
“Beware, brethren, lest there be in any of you an evil heart of unbelief in departing from the living God…” (Hebrews 3:12).
A person straying off the Word will drift into spiritual defect. “Unprincipled” (wicked) men will attempt to lead them away from confidence in the truth. They try to make Christians abandon their relationship with God and His Word. This will blow them off course from God and will shipwreck their souls. They will run their spiritual ship aground.
Instability ends in a distortion of truth and spiritual ruin.
It is possible to fall from soundness in Christ and lose assurance of salvation. False teaching will water down our faith. We cannot lose our salvation, but we can lose the confidence of our salvation (2 Peter 1:10).
A stupid person is an unstable person. Cockamamie Christians are unstable Christians. These are believers who distort Scripture to their ruin. All this starts with ignorance of the Word and ultimately leads to spiritual downfall.
If we run into a difficult situation and do not know Scripture, we will distort the truth that we know. When we find ourselves in a jam, instead of appropriating the principles of God’s Word to our experience, we will jump toward a panacea, a nonbiblical cure-all for our problem.
On the other hand, if we “grow in the grace and knowledge of our Lord and Savior Jesus Christ” (v.18), we will achieve spiritual stability.