Nuggets from "An Urgent Call to a Serious Faith" by Dave Hunt - Truth Is Defined in Doctrine

The doctrine of Christ forms the basis for a victorious life of “love, joy, peace, longsuffering, gentleness, goodness, faith, meekness, temperance” through the power of the Holy Spirit (Galatians:5:22-23 [22] But the fruit of the Spirit is love, joy, peace, longsuffering, gentleness, goodness, faith, [23] Meekness, temperance: against such there is no law.
See All...). What is that doctrine? That Christ is God himself become man to die for our sins. Resurrected and ascended on high, He comes by His Spirit to live in those who open their hearts to Him. Christ likened Himself to a vine that pours its life through us, the branches, to produce fruit in us for the Father. This dynamic union is no mere mystical experience but is itself based upon doctrine,  that is, what we believe and understand of “the truth as it is in Jesus.” John’s declaration that we must abide in the doctrine of Christ elaborates upon Christ’s statement, “Abide in me” (John:15:4Abide in me, and I in you. As the branch cannot bear fruit of itself, except it abide in the vine; no more can ye, except ye abide in me.
See All...). As with Paul, so for us today: the lives we live must spring from the doctrine of Christ and be consistent with it.

So essential is sound doctrine that the Holy Spirit through John commands that those of us who “bring not this doctrine” are not to be received into our houses nor are we to “bid [them] God speed” (2 John 10). This does not mean that we may not invite Jehovah’s Witnesses or Mormons who knock on our doors to come into our homes for a discussion. However we must do so only to evangelize them, making it clear that we oppose their false teachings. This must be our consistent stance toward all who deny the doctrine of Christ, even though they pass for Christian leaders in today’s church.