theologians.(165) Plato and Aristotle, moreover, from the continuous
motion of all matter, inferred a prime cause, an unmoved mover. This is
the so-called _cosmological_ proof, used by different schools in varying
forms.(166) It occupies the foremost place in the systems of the Arabic
Aristotelians, and consequently is dominant among the Jewish philosophers,
the Christian scholastics, and in the modern philosophic schools down to
Kant. It is based upon the old principle of causality, and therefore takes
the mutability and relativity of all beings in the cosmos as evidence of a
Being that is immutable, unconditioned, and absolutely necessary, causa
sui, the prime cause of all existence.

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,