difference between types of experiences

By experience I would mean any awareness of a direct contact with reality. And, because (for us) that contact is always mediated by our own consciousness, it is always the contact of a person with reality, and so always a personal experience, as everyone has said. The purpose of this definition of experience is mainly to distinguish the moment of direct contact from later interpretation, conceptualization, and symbolic expression within a given culture or religious tradition. These later expressions may be more or less impersonal, or at least contain an element which is not as directly personal. The distinction comes in handy in comparative religion when evaluating the nature and meaning of the so-called "mystical" experiences across traditions. The difference between "types" of experience might come down to the different categories we place their interpretations into.

To me, "mystical", "spiritual", and "religious" are at least close synonyms, in the context of dealing with the question of experience. I know that people have drawn distinctions between them, for example as between "religion" meaning primarily well-established, doctrinally presented, institutionalized religious groups, and "spiritual" or "mystical" intended to emphasize the experiential and individual over the doctrinal and institutional. But in context of experience, the distinction doesn't necessarily seem useful to me. The prayerful experience of a roman catholic nun could easily fit all 3 categories, in multiple ways, in my opinion. I'm also not sure I'd absolutize a difference between being in the presence of God and being in union with God, and say the former is religious and the latter mystical, but it also doesn't seem necessary to quibble over terms. How I'd use the words might depend on what I was trying to express. The categories themselves are matters of interpretation, rather than of experience itself, and we invent the categories to fit the needs of what we are trying to communicate.

I don't think mystical (or quasi-mystical) experiences are out of bounds for hardcore atheists and those who subscribe to philosophical materialism.

However, such experiences may take a somewhat different "shape" to those who subscribe to forms of theism or philosophical idealism, such as Advaitists. Nevertheless, the common experience being rooted in psychology is likely to have certain commonalities too.

I can hold out Epicurus' concept of ataraxia (ἀταραξία) as one form of mysticism which fits perfectly with contemporary atheism and materialism. Wikipedia summarises this neatly as "a lucid state of robust tranquility, characterized by ongoing freedom from distress and worry." What I find particularly interesting is that the Epicurean tradition also had a related bodily component of aponia (ἀπονία) which is associated with relaxation of physical muscular tension.

Such were categorised by the Epicureans as "katastematic" (state) pleasure, pleasure felt when being in a particular state, the pleasure that accompanies well-being as such, as opposed to pleasure derived from performing activities and via sensory experience (which are nevertheless not to be devalued). This leads to a refined form of philosophical hedonism in which the pursuit of pleasure/happiness takes on a quasi-spiritual aspect, a far cry from crass hedonism as commonly understood.

Ataraxia was also sought by the Sceptics, who associated it with suspension of judgement of dogmatic beliefs; and by the Stoics, who associated it with the related concept of apatheia (ἀπάθεια), which refers to equanimity and an indifference to fortune which lies outside one's sphere of control. The commonality with many mystics is the necessity of self-discipline to cultivate such mental purification, which leads to ongoing blissful states of mind and freedom from distress. Nevertheless, a neophyte may still experience glimpses of such states.

As I mentioned earlier, though, how such experiences of such states are interpreted depends largely on the belief system they are interpreted through, as in seeing them through a particular lens.