How many times have we heard the phrase "I cannot deny my experience"? This is all the more the cry when it comes to religious experience. But in fact the issue is not the reality or the clarity of the experience, the issue is the source, the content and trajectory of the experience. What distinguishes a good from a bad religious experience in part depends on whether it has come from the one true God, or from some other source. It also depends on what that experience leads, impells, or prompts you to do. 'You shall know the tree by the fruit it bears...." And according to the author of 1 John, there are even specific criteria by which we may be able to tell whether a particular religious experience is from God or comports with the Christian faith.
In his classic commentary on the Johannine Epistles, C.H. Dodd says this about the validity of religious experience:
"We may have the feeling of awareness of God, of union with Him, but how shall we know that such experience corresponds to reality? It is clear that no amount of clearness or strength in the experience itself can guarantee its validity, any more than the extreme vividness of a dream leads us to suppose that it is anything but a dream. If, however, we accept the revelation of God in Christ, then we must believe that any experience of God which is valid has an ethical quality defined by what we know of Christ. It will require with it a renewed fidelity to His teaching and example. The writer does not mean that only those who perfectly obey Christ and follow His example can be said to have the experience of God. That would be to affirm the sinlessness of Christians in a sense which he has repudiated [see 1 Jn. 1]. But unless the experience includes a setting of the affections and will in the direction of the moral principles of the Gospel, it is no true experience of God, in any Christian sense."
In 1 John 2 the Beloved Disciple suggests a series of moral tests to see if one's experience is of God, for example-- does it produce behavior like the behavior of Jesus? Does it lead one to love God with one's whole heart and one's neighbor as self, or is it narcissistic in character? Does it lead to holy living or does it lead to questionable beliefs and behavior? Does it lead to moving on faith, or does it lead to fear-based practices, since the experience of the real love of God casts out all fear? Does it lead to the belief that Jesus is the Son of God come in the flesh, as the Johannine Epistles put it, or to some sort of heterodox belief about Jesus?
At the end of the day what the author of the Johannine Epistles is suggesting is that there are some external tests, tests grounded in what God's Word says and what Christ's character manifests by which we may and should evaluate our experiences including even very genuine religious experiences. As it turns out, the way to tell the difference between heart burn and a heart strangely warmed, both genuine experiences, is by evaluating it by using external and objective criteria. In an affective age, this is all the more crucial because feelings are often deception and a notably bad guide to truth or the goodness of something.