 This model of causality is assumed in some way in every demonstration that it is necessary that a thing that begins to exist have a cause. Most of them presume that the idea of a thing not yet in existence is the idea of the capacity for its existence. This is not the bare logical possibility of something X, but the actual existence of two or more things with the potential to actualize X. Under this conception, it is a contradiction to suppose a thing that begins to exist has no cause, but the key conception is taken for granted. There is no effort to prove the highly contentions notion that a thing that beings to exist must be preceded by the existence of the capacity for its existence.  So the conclusion that a cause is necessary would seem to be the natural product of nothing other than the human mind, a tautology framed from ideas all of which originate in the faculty of  reason.[4]  It is commonly believed to be a necessarily true of the real world but this remains to be justified.