The evidence for faith healing relies not on statistics and scientific procedures, primarily, but on personal testimonies. Testimonies, which are designed to strengthen one’s own faith while convincing or converting an audience, can be faked and dissimulated.
Semantically, a healing testimony or faith claim enacts an exchange between the giver of the message and its recipient. If the recipient doubts, the faith testimony has failed, in a sense, since it has not achieved its goal of converting the listener. If the giver of the message is lying, then even if the listener believes it, this faith healing is untrustworthy.
Nor does quantity of evidence matter so much as quality, when it comes to healing miracles. A multitude can be tricked and deceived, just as a single person of discernment may be sufficient to vouch for the truth of a miracle or faith claim.
Further, proof of spiritual matters — such as healing or prayer – can be quite elusive. One believes in the causality of the Spirit, through prayer or healing, once one receives its benefits. Yet, the mind and ordinary reasoning kick in very soon afterwards. Doubts crowd in and ordinary explanations assert themselves, thus undercutting the validity and credibility of one’s faith or healing testimony.
How then do we decide faith healing claims? It may be that the mode for gaining trust in a faith claim is not unlike our ways for ascertaining a trustworthy character or a reliable experience of love.
The heart can be deceived, yet after some time, and some testing, by our intuition we do know, if we are honest with ourselves. We recognize the one we love, the one who loves us. We can ascertain who is trustworthy. Likewise, we know when faith plays a role in healing; it will be obvious to the heart that is open and discerning.
Some have made use of new scientific paradigms in order to test phenomena like distance healing and the use of thoughts or intentions to provide beneficial outcomes. See, for instance, the interview (below) with Lynne McTaggert, author of The Intention Experiment.
Here are some resources, for your own exploration.
1. Here’s a discussion of the science of healing, prayer, and paranormal experiences by the researcher Larry Dossey : a podcast interview and an older article
2. Here are testimonies of faith claims by Christians:
Christian Scientists: Christian Science Healing Video
Evangelical Christians: Testimonies: Christian Assemblies International
3. Fraudulent Faith Healing
4. Interview with Lynne McTaggert about distance healing and such phenomena: