The lives and writings of the mystics of all great religions bear witness to religious experiences of great intensity, in which considerable changes … - Nyanaponika Thera

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The lives and writings of the mystics of all great religions bear witness to religious experiences of great intensity, in which considerable changes are effected in the quality of consciousness. Profound absorption in prayer or meditation can bring about a deepening and widening, a brightening and intensifying, of consciousness, accompanied by a transporting feeling of rapture and bliss. The contrast between these states and normal conscious awareness is so great that the mystic believes his experiences to be manifestations of the divine; and given the contrast, this assumption is quite understandable. Mystical experiences are also characterized by a marked reduction or temporary exclusion of the multiplicity of sense-perceptions and restless thoughts. This relative unification of mind is then interpreted as a union or communion with the One God. ...
The psychological facts underlying those religious experiences are accepted by the Buddhist and are well-known to him; but he carefully distinguishes the experiences themselves from the theological interpretations imposed upon them. After rising from deep meditative absorption (jhāna), the Buddhist meditator is advised to view the physical and mental factors constituting his experience in the light of the three characteristics of all conditioned existence: impermanence, liability to suffering, and absence of an abiding ego or eternal substance. This is done primarily in order to utilize the meditative purity and strength of consciousness for the highest purpose: liberating insight. But this procedure also has a very important side effect which concerns us here: the meditator will not be overwhelmed by any uncontrolled emotions and thoughts evoked by his singular experience, and will thus be able to avoid interpretations of that experience not warranted by the facts.
Hence a Buddhist meditator, while benefiting from the refinement of consciousness he has achieved, will be able to see these meditative experiences for what they are; and he will further know that they are without any abiding substance that could be attributed to a deity manifesting itself to his mind. Therefore, the Buddhist’s conclusion must be that the highest mystical states do not provide evidence for the existence of a personal God or an impersonal godhead.