7. The Mohammedan theologians added a new element to the discussion. In their endeavor to prove that the world is the work of a Creator, they pointed as evidence to the multiformity and composite structure, the contingency and dependency of the cosmos; thus they concluded that it must have been created, and that its Creator must necessarily be the one, absolute, and all-determining cause. This proof is used also by Saadia and Bahya ben Joseph.(167) Its weakness, however, was exposed by Ibn Sina and Alfarabi among the Mohammedans, and later by Abraham ibn Daud and Maimonides, their Jewish successors as Aristotelians. These proposed a substitute argument. From the fact that the existence of all cosmic beings is merely possible,—that is, they may exist and they may not exist,—these thinkers concluded that an absolutely necessary being must exist as the cause and condition of all things, and this absolutely unconditioned yet all-conditioning being is God, the One who _is_.(168) Of course, the God so deduced and inferred is a mere abstraction, incapable of satisfying the emotional craving of the heart. 8. While the cosmological proof proceeds from the transitory and imperfect nature of the world, the _ontological_ proof, first proposed by Anselm of Canterbury, the Christian scholastic of the XI century, and further elaborated by Descartes and Mendelssohn, proceeds from the human intellect. The mind conceives the idea of God as an absolutely perfect being, and, as there can be no perfection without existence, the conclusion is that this idea must necessarily be objectively true. Then, as the idea of God is innate in man, God must necessarily exist,—and for proof of this they point to the Scriptural verse, “The fool hath said in his heart, there is no God,” and other similar passages. In its improved form, this argument uses the human concept of an infinitely perfect God as evidence, or, at least, as postulate that such a Being exists beyond the finite world of man.(169) Another argument, rather naïve in character, which was favored by the Stoics and adopted by the Church fathers, is called _de consensu gentium_, and endeavored to prove the reality of God’s existence from the universality of His worship. It speaks well for the sound reasoning of the Jewish thinkers that they refused to follow the lead of the Mohammedans in this respect, and did not avail themselves of an argument which can be used just as easily in support of a plurality of gods.(170)