A critique of a system, in order to be meaningful and important for one who adheres to the system, must be in accordance with the elements of the system in question, ie. it must be shown that the system in question is self-referentially incoherent, rather than being different or in contradiction to the system we ourselves affirm.
A belief-set, may contain elements which serve to increase one's belief in the belief-set itself, eg, religious experience in regards to the religion affirmed, and obviously, competing belief-sets may have elements which serve to increase the belief in the belief-set, but this fact is hardly an objection.
In order to justify my beliefs, I can only rely on the beliefs I already hold, ie. in order for me to justify all the propositions which I affirm to be true, I must use propositions which I hold to be true. This is the consistent, and necessarily circular nature of a consistent epistemology. To use an analogy, the quine axiom is a set, which is an element of itself. Or if you prefer, the premises which I use to justify my beliefs, are themselves believed, and therefore my belief-set is self-referential.
The diversity of beliefs brought about seems to tell me that this belief producing mechanism is terribly unreliable at best.
A 'belief-producing mechanism', can only be a belief producing mechanism, if it is already regarded as reliable. To say that it is unreliable, is to provide an external critism of the system of belief, a criticism irrelevant to those who adhere to the system in question. Rather, such a criticism as regards the impotence of the belief-producing mechanism, can only be relevant if it is an element of the system, that it can withstand the 'Uniqueness of Conceptual Framework Objection'. So long as the system is not regarded to be able to withstand the UCFO, then the belief-producing mechanisms need only be helpful for those who affirm the system. To use the example of reason, it is reasonable to affirm the validity of reason, and a reasonable justification for reason, is all that is required for those that believe that in the use of reason. For complete philosophical skeptics, no argument will suffice, and it is understood that a skeptic of reason, can not be persuaded by reasonable argumentation. Likewise, it is understood that a skeptic of religion can not be persuaded by reports of religious experience.
It may be argued that although a person can reasonably use reason, it is arbitrary for someone to justify her religious belief, upon her religious experience because others of different religious persuasion may have categorically similar experiences. This however, is to ignore the ontology of the experience, as understood by the religious person. It is logically prior for the skeptic to demonstrate that the experiences are in fact categorically similar, and to do this, an internal critique of the belief system is required.
We must face the problem of the logical prioricity of metaphysics to epistemology, or vice versa, and this is a topic which, although related, needs a thread of it's own.
kind regards
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In case there is someone who is not aware of what the Uniqueness of Conceptual Framework Objection, is:
http://www.iep.utm.edu/trans-ar/#H5Where I have referred to it, I specifically mean that noting that there are people of different religious belief, many of whom find their experience to be 'belief-producing', the fact that different and often contradictory beliefs are similarly justified, can only be a valid objection if it is also believed that a coherent theory disproves the possibility of other theories being correct, ie. a non-wholistic coherency theory of truth.