These people have the spirit of truth promised to help guide them on their path and it is these who are the true body of Christ.
Many will assert they are true Christians or of the body but, the one differentiating point between those who are and are not is that those chosen will have the helper who can answer when asked by the believer about God. When Christ walked the earth he separated the two types of people by the use of parables.
Matt 13:
10And the disciples came, and said unto him, Why speakest thou unto them in parables?
11He answered and said unto them, Because it is given unto you to know the mysteries of the kingdom of heaven, but to them it is not given.
12For whosoever hath, to him shall be given, and he shall have more abundance: but whosoever hath not, from him shall be taken away even that he hath.
13Therefore speak I to them in parables: because they seeing see not; and hearing they hear not, neither do they understand.
14And in them is fulfilled the prophecy of Esaias, which saith, By hearing ye shall hear, and shall not understand; and seeing ye shall see, and shall not perceive:
15For this people's heart is waxed gross, and
their ears are dull of hearing, and their eyes they have closed; lest at any time they should see with
their eyes, and hear with
their ears, and should understand with
their heart, and should be converted, and I should heal them.
Now the spirit of truth guides the believer who is of the body and does not guide those who are not.
John 16:12 I have yet many things to say unto you, but ye cannot bear them now. 13 Howbeit when he, the Spirit of truth, is come, he will guide you into all truth: for he shall not speak of himself; but whatsoever he shall hear, that shall he speak: and he will shew you things to come.