Sometimes people wonder if anyone can definitively say or know whether someone is a Christian or not. Let us consider the following verses:
Then said Jesus to those Jews which believed on him, If ye continue in my word, then are ye my disciples indeed;
Now the just shall live by faith: but if any man draw back, my soul shall have no pleasure in him.
They [antichrists] went out from us, but they did not really belong with us; for if they were really part of our group, they would no doubt have continued with us: but they left; this shows that none of them really belonged with us.
(1 John 2:19)
For we are made partakers of Christ, if we hold the beginning of our confidence steadfast unto the end;
The verses above soundly demonstrate that persons who do not continue in His Word (i.e. standing against God’s law) are not His followers. This is different from the person who acknowledges God’s law as perfect and yet falls short; such individuals are recognized by their willingness to admit sin while submitting to the Word of God. However, for the person with a seared conscience that declares good is evil and evil is good (Isaiah 5:20), and speaks lies in hypocrisy (1 Timothy 4:1-2), we can rest assure that according to the Words of Christ they are not really his followers.