(This is from my book Praying: Reflections on 40 Years of Solitary Conversations with God.)
I believe the question, “Does prayer work?”, can only be answered by those who have committed themselves to a life of praying.
I have kept journals recording my prayer life since 1977. My journals total over 3500 pages. I have had many incidences where the best explanation for an event, as far as I can tell, is that it is an answer to my prayers.
I have much personal experience with praying. This is important to me because of a deep philosophical belief I have, which is: experience, not theory, breeds conviction. So, I’m going to be praying today, and tomorrow. I would not pray if I thought it did not work. (This reasoning is by via negativa.)
It is important for me to say this. I don’t expect my experience to convince others. But this is my experience, just as you have your experiences; therefore, I stand convinced. Call this an existential reason, without which I have no idea why I would pray (To religiously fake it? To impress others?).
I have taught praying to many people. My estimate is that I have taught at least 3500 pastors and Christian leaders about praying. 1500 of them have engaged in six weeks of praying, one hour a day, five days a week. They have kept journals recording their prayer experiences. They have sent their journals to me. I have read them. These students have been, literally, from all over the world. A few have invited me to their countries to teach prayer to their people and colleagues. I have a broad, deep, data base of people who committed themselves to actually praying. These people tell of experiences and events that deepen my already-held conviction that prayer works.
I have studied, and taught, the history of prayer and praying. I am familiar with the praying lives of many historical figures. The end result of my studies has been to inspire me to continue to pray.
Scholarly, empirical studies of prayer and praying support my existential belief in the veridicality of praying. Such as, to cite but two, Testing Prayer: Science and Healing, by Candy Gunther Brown; and The Psychology of Prayer: A Scientific Approach, by Bernard Spilka and Kevin Ladd.
I have read countless counterexamples to my belief that prayer works. I’ve read innumerable atheistic (and other) arguments claiming that the statement Prayer works is false. I began reading this counter-literature in 1971, as an undergraduate philosophy student. (Beware - philosophy makes you read opposing ideas!) I have little sympathy with atheists who have never had a praying life and, out of their non-engagement, believe they have falsified the claim that prayer works. Their theoretical arguments, which are logical manifestations of their worldview, do not dissuade me.
I have also read many books by ex-theists who claim to have prayed like I have but found no reciprocity. I am sympathetic towards these testimonies. But note this: since my personal testimony is to the efficacity of praying, absence-testimonies do not persuade me any more than my testimony persuades an ex-believer.
Jesus believed praying works. I believe Jesus is God incarnate. Therefore, I believe praying works. A major portion of my adult life has been spent immersed in Christological studies. I remain convinced that Jesus is who he claims to be. Note the pronoun ‘I’. I know why I believe praying works. Obviously I do believe praying works, since I continue doing it. Here personal knowledge is important (see Kierkegaard, and Michael Polanyi on "tacit knowledge.").
I believe prayer works because I believe a personal God exists. If I did not believe this I would not pray, period. My praying life is a function of (is in direct proportion to) my belief in God. I have a deep, experiential, and philosophical belief that, not only does God exist as a personal agent, but God is good, God loves me, and God is working all things together for good. Because I am certain, as well as happy, that I am not the all-knowing, all-loving God, I know I do not have full epistemic access to what God is doing. I have prayed for things that, from my POV, seem unanswered. At this point my properly basic belief in God helps me trust that my prayers are not going unheard.