There is a charge which has been very often brought against the _a priori_ proofs, but which may be at once set aside as incorrect. It has been alleged that they proceed on forgetfulness of the truth that the Divine existence is the first and highest reality, and therefore cannot be demonstrated from anything prior to or higher than itself. But in no case that I know of have those who adopted what they supposed to be the _a priori_ line of argument been under the delusion that the ground of the existence of God was not in Himself, but in something outside of or above Himself, from which His existence could be deduced. Such a notion is, in fact, so self-contradictory, that no sane mind could deliberately entertain it. It would imply that theism could be founded on atheism. Whatever _a priori_ proof of the Divine existence may be, it has certainly never been imagined by those who employed it to be demonstration from an antecedent necessary cause.[48] [48] See Appendix XXXVII. _A priori_ proof is proof which proceeds from primary and necessary principles of thought. From its very nature it could only appear at a comparatively late period in the history of intelligence. It is only a profound study of the constitution of thought, only a refined reflective analysis of consciousness into its elements, which can bring to light the principles which necessarily underlie and govern all intellectual activity; and it is only on these principles that _a priori_ proof is based. As these principles never exist in an absolutely pure form, as what is universal and necessary in thought is never found wholly apart from what is particular and contingent, no absolutely pure _a priori_ argumentation need be looked for, and certainly none such can be discovered in the whole history of speculation.