There is, in my book, a critical and important distinction to be made between spiritual man and religious man. Some will argue that the terms spiritual and religious can be used interchangeably. Others, including myself, will argue that the term spiritual is to be associated with the private realm of introspection and experience whereas religious is to be associated with membership in a public institution which includes participation in formal rituals and doctrines.
However, the distinction between the private, spiritual person and the public, religious person still remains, too, superficial. As I see it, the difference between spiritual man and religious man is much more striking. It is like the difference between energy and matter. In this regard, we can view matter as dense, compacted energy, but nevertheless energy which is dynamic; appearing to exert influence on matter. But from the perspective of matter there appears to be an unresolved dualism; moreover, matter cannot act on itself.
While the analogy of energy and matter is very limited it does help to illustrate the difference between spiritual man and religious man. The spiritual man is at ease in the immaterial whereas the religious man is drawn to matter. He believes in a matter creator, a demiurge/Isvara; the spiritual man sees the universe as a projection of spirit or as the Lankavatara Sutra puts it, the external world exists only in conformity with Mind-only. In other words, only Mind exists, Mind being spirit.
Drawing from Buddhism, our spiritual man is none other than those beings (arya) who resonate with the unconditioned essence or at least have faith in it. They understand that there is a significant distinction to be made between the unarisen essence and the arisen composition, as one might distinguish between raw gold and a fabricated gold lion.
Our religious man is at home in a material world despite its fragility, suffering and finitude; which includes his own repeated failure to rise above his self-willed ignorance, violence, and greed. Still, in all truth, spirituality supersedes the religious man which means it will, in time, undermine the religious. Why is this so? The religious man has unconsciously made spirit God, having to place his God beyond himself just as spirit, which is unconditioned, is beyond all conditionality. The God the religious man worships and fears, unbeknownst to him, is his own spiritual nature which he cannot bear to look at; which, paradoxically, he always suppresses.
The religious can only push away spirit so as to conceal it, completely. But as a result of this pushing away, more and more, the religious becomes the dead letter and the sepulcher. This is seen in both the life of Gautama the Buddha and Paul the Apostle, both of whom represent the coming of the spiritual man. Neither were religious as we would like to believe. Foremost, both had profound mystical experiences which shaped their teachings; which pointed beyond the material and the religious. Both brought a new vision. From the spiritualization of Brahmanism emerged Buddhism; from the spiritualization of Judaism emerged Christianity.