I'm going to comment on some objections to the argument from religious experience by atheist philosopher Richard Gale. His foil is Alston's Perceiving God. I won't be using Alston's monograph as my own frame of reference. I'm just exploitting Gale's criticisms as a launchpad:
Necessarily, any cognitive perception is a veridical perception of an objective reality. It now will be argued that it is conceptually impossible for there to be a veridical perception of God…from which it follows by modus tollens that it is impossible that there be a cognitive religious experience. My argument for this is an analogical one that, like those for the cognitively of religious experiences, takes sense experience to be the paradigmatic member of the analogy. A veridical sense perception must have an object that is able to exist when not actually perceived and be the common object of different sense perceptions. For this to be possible, the object must be housed in a space and time that includes both the object and the perceiver. It is then shown that there is no religious experience analogue to this concept of objective existence, there being no analogous dimensions to space and time in which God, along with the perceiver, is housed and which can be invoked to make sense of God existing when not actually perceived and being the common object of different religious experiences. Because of this big disanalogy, God is categorically unsuited to serve as the object of veridical perception, whether sensory or nonsensory.
In arguing that it is impossible for there to be a veridical religious experience of an objective reality, I am not engaging in an objectionable form of chauvinism by requiring that the sort of objective existence enjoyed by the objects of veridical sense experiences, physical objects, hold for all objective existents. I am happy to grant that there are objective realities that do not occupy space and/or time nor any analogous dimensions, such as the denizens of Plato's nonspatiotemporal heaven; and God might very well be among these objectively existent abstract entities. What is impossible is that there be any veridical perception of one of them, even of the intellectual sort describe by Plato in the Phaedrus, according to which we "see" them with our mind's eye… R. Gale, On the Nature and Existence of God (Cambridge, 1996), 326-27.
i) God is essentially imperceptible. By that I mean, God exists outside space and time. In that respect, it isn't possible to perceive God in himself using the five senses. The question is whether we can perceive an effect of God. By the same token, whether we can perceive a self-representation of God. The effect or representation can occupy our visual field, or be heard, even if God in himself remains imperceptible. That isn't just analogous to sensory perception–that is sensory perception (of the divine).
Paradigm-cases include theophanies (e.g. Ezekiel 1) and God's audible voice. Let's say a theophany is an audiovisual (and perhaps tactile) representation of God. There's a genuine external stimulus which the observer perceives. It ccould be photographed. It's physical in the sense that lightwaves and sound waves are physical.
God doesn't have a natural voice. But God can simulate vocalization. The auditor would hear sentences, although no speaker was visible. The sound would originate outside his mind. Stimulate his eardrums.
ii) The divine object (e.g. source of theophanies) can exist when not actually be perceived. The effect or representation can be the common object of different sense perceptions.
iii) Since, however, the mode of perception needn't be sensory, but only be analogous to sensory perception, it needn't satisfy all the conditions of sensory perception. In that regard, take revelatory dreams. Dreams simulate physical space. Dreams simulate sensory perception.
Normally, dreams are the product of the dreamer's imagination, but in principle a dream can originate outside the dreamer's mind. Suppose telepathy exists. Suppose another agent causes someone to have a particular dream.
iv) We need to distinguish between perception and perceptual inferences. Suppose I'm driving toward the ocean. There comes a point when I notice that trees on the hillside are permanently bent. They face away from the coast. They grew bent due to the chronic onshore breeze. I therefore conclude that I must be approaching the ocean. This is two steps removed from the percept. I infer that an onshore breeze caused the trees to grow bent, and I infer that the ocean generated the onshore breeze. How different is that from an unmistakable answer to prayer?
Because these objects are nondimensional, they will be disanalogous to empirical particulars in several important respects. First, they will have radically different grounds of individuation. Whereas empirical particulars are individuated by their position in nonempirical dimensions, they are not.
Another invidious consequence of their nondimensionality is that no analogous explanation can be given for how they can exist unperceived and be common objects of different perceptions to that which was previously given for empirical particulars. Whereas we could explain our failure to perceive an empirical particular, as well as our perceiving numerically one and the same empirical particular, in terms of our relationship to it in some nonempirical dimension, no such analogous explanation can be offered for our failure to perceive God and the like, or our perceiving numerically one and the same God. This means that it is impossible in principle to distinguish between, for example, mystical experiences that are numerically one and the same undifferentiated unity and the like and those that are merely qualitatively similar ones. Ibid. 341.
i) I don't now what he means when he says "empirical particulars are individuated by their position in nonempirical dimensions." Wouldn't physical objects be individuated in physical space?
ii) Consider how objects are individuated in dreams. Even though the grounds of individuation are different, the result is the same. We see distinct objects against a contrastive background when we dream. We can hear dream characters speak to us.
iii) We perceive God when God produces a symbolic self-representation–or an effect which we infer to signify God. We don't perceive God when he doesn't produce that emblematic external stimulus.
iv) In the case of revelatory dreams, we perceive God when God inspires a revelatory dream, and we don't perceive him when we have ordinary dreams. A revelatory dream needn't be a common object of perception, although God is able to inspire two or more people to have the same dream.
v) As to whether it's impossible in principle to distinguish between perceptions of one and the same God and merely similar impressions, which may not be numerically the same, that depends, in part, on how stringently Gale defines veridicality. It's easy to concoct Matrix-like undercutters in which no perception is veridical. Where you can never distinguish reliable perception from illusion. Presumably, Gale doesn't wish to set the bar that high.
vi) Perhaps the question is how do we verify that these prima facie perceptions of God are in fact about God? The answer depends on the nature of the perception. For instance, a revelatory dream might disclose verifiable information that the dream didn't initially have at his disposal. It had to come from an outside source. Same thing with an audible voice.
A theophany might utilize religious symbolism. And unless you're open to ufology, there'd be no naturalistic alternative explanation.
vii) Take the case of recurring dreams. These are nonempirical, yet we remember seeing that dreamscape before.
viii) Perhaps Gale would ask how we distinguish a theophany from a psychotic hallucination. But is that a question for the observer? If the observer is in fact psychotic, then he's in no condition to diagnose himself, no matter how good the criteria. And that's true for mental illness in general. It's not confined to visions. Crazy people can't test their perception of reality since their distorted perceptions would extend to the test. If that's grounds of skepticism, the skepticism infects perception in general. So that objection either proves too much or too little.
ix) I'm not suggesting these paradigm-examples (theophany, audible voice, revelatory dream) are ways in which people typically perceive or experience God. I simply use them to establish a principle.