As a starting point, let me point out that I am not a Christian, and what follows are merely my own views. My additional qualifier is that if you are not a Christian, then the rest of the post may make no sense to you and you can stop reading right around here. (This qualifier is similar to the one that I had previously used, when I wrote about TAR from the Buddhist perspective).
No person who considers himself a true Christian can at the same time logically dismiss TAR. The Christian faith is incompatible with a disbelief in TAR. This is because prayer and the effects of prayer are an integral aspect of Christianity, and prayer is also a fundamental example of thought affecting reality.
The Bible has numerous examples of people calling on God for help or guidance. In response, the help or guidance comes, and specific events begin occurring in reality.
Sometimes these events are mild and subtle, and they occur in the person's "internal" reality. For example, he receives, or he believes he receives, a message or instruction from within. Sometimes the events are big and unmistakeable, and they occur in the "external" reality (a drastic example would be the ten major calamities which Moses, through God, inflicted on Egypt).
Events can also be drastic and powerful within the person's internal reality (such as a very direct, "loud" message or instruction from within) or they can be mild and subtle in the external reality (for example, the person prays for help on a personal problem, and a few small events then happen in his external reality to solve his problem).
As a Christian, you probably have personally experienced, and/or know of other fellow Christians who have experienced, such events, in the four main permutations as described above. In other words, there are many examples - they are not merely biblical or historical.
So far, we have seen that prayer is a form of thought. You can regard it as a deliberate form of thought that a Christian adopts, when he seeks to establish a direct connection with the divine. What about other kinds of thoughts, that is to say, the kind of thoughts that a Christian thinks, not when he is praying, but merely going around his daily routine - driving, working, showering, feeding the cat etc?
The Christian God, as described in the Bible, is an omniscient one. Okay, that is subject to some debate among the theologians (there are some technical complications arising in connection with free will) but let's just make that assumption for the purposes of the present discussion.
The basic point is that even if you're not praying, the Christian God knows what's on your mind, yes? If you wish to have a much more direct connection with God, you will pray. But even if you don't, God knows what you're thinking, and what's happening in your life, and for that matter, just about everything else in your reality (think falling sparrows - Matthew 10:29).
Once you see the interrelationships, you will understand better the more "absolute" types of argument about how thought affects reality. Within the Christian framework, we could say that since every one of your thoughts is heard by God, and God has omnipotent powers over everything in your reality, every thought of yours has at least the potential to affect some aspect of your reality, because God can orchestrate it.
And perhaps you will even understand why the Buddhists place emphasis on disciplining the mind and the kind of thoughts that go through it. For example, in Buddhism, it is insufficient to refrain from doing cruel acts - one must endeavour not to think cruel thoughts at all.
(For Christians, I would add this - even if God always knows what's on your mind, it's when you pray that He knows you really want His attention. So that's when He'll give his attention to you. So pray, ok? Don't stop praying just because He always knows what's on your mind anyway).
One big difficulty that many Christians will have with TAR is that they may feel slightly appalled at the idea of altering their thoughts so as to get what they desire in reality - especially if what they desire are materialistic or physical or "selfish" in nature (for example sex, money, power, material things etc). The other big difficulty is that God, as seen from the Bible, has His own distinct personality, ideas and plans. He doesn't necessarily give you what you want - instead He may have his own very specific plans on what you should be doing and where you should go (think Jonah and the whale).
These are points which I will discuss in future (this post is long enough). Suffice to say for now that a lot of the difficulty stems from the idea that you are not God - that there is a separation between "you" and "God" and that there could be a difference between what you want and what He wants. In my opinion, this difficulty is an illusion, because the "you" does not even exist - there is in fact no separation between "you" and the rest of reality, or beween "you" and "God", whatever that is. But as I said, more on that, another time. It's a complex idea, not explainable in just a few short paragraphs.
We'll end today's post with some biblical verses, which I invite the Christians to reread and think about, with TAR in mind. This is taken from Matthew 7:7 and 7:8, and is part of one of the longest, most extensive set of public teachings (I think) given by Jesus, as recorded in the New Testament:
"Ask, and it will be given to you; seek and you will find; knock, and it will be opened to you. For everyone who asks receives, and he who seeks finds, and to him who knocks it will be opened.Don't take my word for it, on anything I've said in this article - I'm not even Christian, remember? This post is just food for thought. Go think about it for yourself. If you still have lots of questions after that, try asking your own Christian God directly for the answers. That, in my experience, tends to work quite well too. Ask, and it will be given.
Or what man is there among you who, if his son asks for bread, will give him a stone? Or if he asks for a fish, will he give him a serpent?
If you then, being evil, know how to give good gifts to your children, how much more will your Father who is in heaven give good things to those who ask Him!"