The apostle Paul prophesies of an apostasy in II Thessalonians 2:3, 9-12, and he prefaces it with a warning against being deceived. The great apostasy may already be fully underway, spurred by the rising tide of deception in society. With so much information available (Daniel 12:4)—along with so many ways to manipulate it—men find it extremely easy to deceive millions instantly. This is especially true for those who do not really believe the true source of knowledge, God and His Word. Thus, after subtle doctrinal changes, many of the brethren have fallen away.
The "coming of the lawless one," however, is still future. His rise to prominence and power will be accompanied by incredible miracles, but they will be false signs and wonders, lies produced by Satan to appear as if they are of God (see Revelation 13:11-15). He will use "all unrighteous deception," a hint that what he does and says will appear as righteous, yet someone who knows and loves the truth can see through it and avoid being deceived.
Satan will really pull out all the stops to deceive as many as possible, especially the called sons of God. The "lawless one" will be so slick that "all who dwell on the earth will worship him, whose names have not been written in the Book of Life of the Lamb slain from the foundation of the world" (Revelation 13:8). But, as Paul writes elsewhere, if we hold fast to "the pattern of sound words" that we learned, if we guard the truth, we will not be deceived.
Paul repeats these instructions to the Thessalonians in this context:
Therefore, brethren, stand fast and hold the traditions which you were taught, whether by word or our epistle. (II Thessalonians 2:15)
The key to resisting deception is being convicted of the truth! The truth is what was first revealed to the apostles. As Jude puts it, "Contend earnestly for the faith which was once for all delivered to the saints" (Jude 3).
As they saw the first-century apostasy coming, all the apostles warn about deceivers and urge the brethren to be certain of and stick to the doctrines of God. It is our surest hedge against being caught up in the deceptions of the end time that are already upon us.