~ Adapted from email correspondence ~
Faith is certainty. It is so certain that Jesus said if you pray in faith you would believe that you have received what you asked for before you actually attain it. When the devil attacks you and you doubt, that means his attack is beginning to be successful. Fight it and kill the doubt. Faith and doubt are not feelings as such but qualities of thought. Fear might be a feeling that arises from doubt.
The Reformed and Evangelicals are very fond of making excuses in this area. They would probably condemn Jesus Christ himself as one of those fanatical “faith teachers.” They might indeed suggest that you can doubt and still be full of faith, or even say that doubt is good. Jesus would loudly rebuke them. No, doubt is bad, always bad. Peter feared, and he sank. James said that if you waver, do not think that you will receive anything from the Lord. The Pentecostals and Charismatics are overall far more faithful to Scripture in this area.
These are generalizations that do not apply to every particular case. There are counterexamples from each side. And although I state the overall situation as I perceive it, the truth is that I could not care less which tradition wins and which one loses. I do not want to take a side and say, “I am of this one!” or “I am of that one!” Neither the Reformed and Evangelicals nor the Pentecostals died to redeem me from sin and endued me with power from heaven. Jesus Christ alone did these things. I will follow him. The rest can come along or they can burn in hell.
Jesus taught that if you even have a mustard seed faith, nothing will be impossible for you. Christians have often twisted this to mean that you can have 1% faith and 99% doubt! This is a demonic perversion of the teaching. No, Jesus said, “If anyone…does not doubt in his heart but believes that what he says will happen, it will be done for him” (Mark 11:23). If you waver, do not think that you will get anything from the Lord.
Of course, sometimes God shows mercy, as when Jesus rescued him while Peter was sinking. But without faith, a man cannot expect to receive, although he still might receive despite his doubts because of God’s sovereign kindness. In any case, rather than making excuses and twisting Scripture so that everyone will feel better, we should accept what Jesus taught on faith, condemn our own unbelief, and strive to attain to the level he commanded.
If you pray full of faith, you will know it, and you will not need to ask anyone, and no one will be able to convince you otherwise.