forms on the other hand come and go. Form does not change any more than matter. The changing thing is the composite
of matter and form, and change means separation of the actual components of which one, the form, disappears and
makes room for its opposite. In a given case, say, when a statue is made out of a block of marble, the matter is the
marble which lost its original form and assumed the form of a statue. In this case the marble, if you take away both the
previous form and the present, will still have some form if it is still marble, for marble must have certain qualities if it is to
be marble. In that case then the matter underlying the change in question is not pure matter, it is already endowed with
some primitive form and is composite. But marble is ultimately reducible to the four elements, fire, air, water, earth, which
are simpler; and theoretically, though not in practice, we can think away all form, and we have left only that which takes
forms but is itself not any form. This is matter.
Here the reader will ask, what kind of thing is it that has no form whatsoever, is it not nothing at all? How can anything
exist without being a particular kind of thing, and the moment it is that it is no longer pure matter. Aristotle's answer is that
it is true that pure matter is never found as an objective existence. Point to any real object and it is composed of matter
and form. And yet it is not true that matter is a pure figment of the imagination; it has an existence of its own, a potential
existence. And this leads us to another important conception in the Aristotelian philosophy.
Potentiality and actuality are correlative terms corresponding to matter and form. Matter is the potential, form is the
actual. Whatever potentialities an object has it owes to its matter. Its actual essence is due to its form. A thing free from
matter would be all that it is at once. It would not be liable to change of any kind, whether progress or retrogression. All
the objects of our experience in the sublunar world are not of this kind. They realize themselves gradually, and are never
at any given moment all that they are capable of becoming. This is due to their matter. On the other hand, pure matter is
actually nothing. It is just capacity for being anything, and the moment it is anything it is affected with form.
It is clear from this account that matter and form are the bases of sublunar life and existence. No change, no motion
without matter and form. For motion is presupposed in all kinds of change. If then all processes of life and death and
change of all kinds presuppose matter and form, the latter cannot themselves be liable to genesis and decay and
change, for that would mean that matter is composed of matter and form, which is absurd. We thus see how Aristotle is
led to believe in the eternity of matter and motion, in other words, the eternity of the world processes as we know them.
Motion is the realization of the potential qua potential. This is an Aristotelian definition and applies not merely to motion in
the strict sense, i. e., movement in place, or motion of translation, but embraces all kinds of change. Take as an example
the warming of the air in a cold room. The process of heating the room is a kind of motion; the air passes from a state of
being cold to a state of being warm. In its original state as cold it is potentially warm, i. e., it is actually not warm, but has
the capacity of becoming warm. At the end of the process it is actually warm. Hence the process itself is the actualization
of the potential. That which is potential cannot make itself actual, for to make itself actual it must be actual, which is
contrary to the hypothesis of its being potential. Potentiality and actuality are contradictory states and cannot exist side
by side in the same thing at the same time in the same relation. There must therefore be an external agent, itself actual,
to actualize a potential. Thus, in the above illustration, a cold room cannot make itself warm. There must be some agency
itself actually warm to cause the air in the room to pass from cold to warm. This is true also of motion in place, that a
thing cannot move itself and must be moved by something else. But that something else if itself in motion must again be
moved by something else. This process would lead us to infinity. In order that a given thing shall be in motion, it would be
necessary for an infinite number of things to be in motion. This is impossible, because there cannot be an infinite number
of things all here and now. It is a contradiction in terms. Hence if anything is to move at all, there must be at the end of
the finite chain a link which while causing the next link to move, is itself unmoved. Hence the motion existing in the world
must be due ultimately to the existence of an unmoved mover. If this being causes motion without being itself in motion it
does not act upon the bodies it moves as one body acts upon another, for a body can move another body only by being
itself in motion. The manner in which the unmoved mover moves the world is rather to be conceived on the analogy of a
loved object moving the loving object without itself being moved. The person in love strives to approach and unite with
the object of his love without the latter necessarily being moved in turn. This is the way in which Aristotle conceives of
the cause of the world's motion. There is no room here for the creation of the world. Matter is eternal, motion is eternal,
and there is an eternal mind for the love of which all motions have been going on, eternally.
The unmoved mover, or God, is thus not body, for no body can move another body without being itself in motion at the
same time. Besides, all body is finite, i. e., it has a finite magnitude. A body of infinite magnitude is an impossibility, as the
very essence of body is that it must be bounded by surfaces. A finite body cannot have an infinite power, as Aristotle
proves, though we need not at present go into the details of his proof. But a being which causes eternal motion in the
world must have an infinite power to do this. Hence another proof that God is not corporeal.
If God is not subject to motion, he is not subject to change of any kind, for change involves motion. As matter is at the
basis of all change God is without matter, hence he is pure form, i. e., pure actuality without the least potentiality. This
means that he is what he is wholly all the time; he has no capacities of being what he is at any time not. But if he is not
corporeal, the nature of his actuality or activity must be Thought, pure thinking. And the content of his thought cannot
vary from topic to topic, for this would be change, which is foreign to him. He must be eternally thinking the same
thought; and the highest thought it must be. But the highest thought is himself; hence God is pure thought thinking
himself, thought thinking thought.
The universe is in the shape of a sphere with the earth stationary in the centre and the heavens revolving around it
exactly as appears to us. The element earth is the heaviest, hence its place is below or, which is the same thing, in the
centre. This is its natural place; and its natural motion when away from the centre is in a straight line toward the centre.
Water is the next heaviest element and its natural place is just above earth; hence the water in the world occupies a
position spherical in shape round about the earth, i. e., it forms a hollow sphere concentric with the earth. Next comes
the hollow sphere of air concentric with the other two. Its natural motion when away from its place in the direction of the
earth is in a straight line toward the circumference of the world, not however going beyond the sphere of the lightest
element of all, namely, fire. This has its natural place outside of the other elements, also in the form of a hollow sphere
concentric with the other three. Its natural motion is in a straight line away from the centre of the world and in the
direction of the circumference. Our earth, water, air and fire are not really the elements in their purity. Each one has in it
also mixtures of the other three elements, the one which gives it the name predominating.
All minerals, plants and animals are formed from these four elements by various combinations, all together forming the
sublunar world, or the world of generation and decay. No individual thing in this world is permanent. All are subject to
change and to ultimate destruction, though the destruction of one thing is the genesis of another. There is no
annihilation.
The causes of the various combinations of the elements and the generation and destruction of mineral, plant and animal
resulting therefrom, are the motions of the heavenly bodies. These are made of a purer substance than that of the four
elements, the ether. This is proven by the fact that the heavenly bodies are not subject to change or destruction. They
are all permanent and the only change visible in them is change of place. But even their motions are different from those
of the four elements. The latter are in a straight line toward the centre or away from it, whereas the heavenly bodies
move in a circle eternally around the centre. This is another proof that they are not composed of the same material as
sublunar bodies.
The heavens consist of transparent spheres, and the stars as well as the planets are set in them and remain fixed. The
motions of the heavenly bodies are due to the revolutions of the spheres in which they are set. These spheres are hollow
and concentric. The outermost sphere forming the outer limit of the universe (the world is finite according to Aristotle) is
studded with the fixed stars and moves from east to west, making a complete revolution in twenty-four hours. This motion
is transmitted to the other spheres which carry the planets. Since, however, we notice in the sun, moon and the other
planetary bodies motions in the contrary direction in addition to that from east to west, there must be other spheres
having the motions apparent to us in the positions of the planets borne by them. Thus a given body like the sun or moon
is set in more than one sphere, each of which has its own proper motion, and the star's apparent motion is the resultant
of the several motions of its spheres. Without entering into further details concerning these motions, it will be sufficient
for us to know that Aristotle counted in all fifty-five spheres. First came the sphere of the fixed stars, then in order the
spheres of Saturn, Jupiter, Mars, Mercury, Venus, Sun, Moon.
God himself sets the outer sphere in motion, or rather is the eternal cause of its motion, as the object of its desire; and in
the same way each of the other motions has also its proper mover, likewise a pure form or spirit, which moves its sphere
in the same incorporeal and unmoved manner as God.
Thus we have in the supra-lunar world pure forms without matter in God and the spirits of the spheres, whereas in the
sublunar world matter and form are inseparable. Neither is found separately without the other.
In man's soul, however, or rather in his intellect we find a form which combines in itself the peculiarities of sublunar as
well as celestial forms. When in contact with the human body it partakes of the nature of other sublunar forms exhibiting
its activity through matter and being inseparable from it. But it is not destroyed with the death of the body. It continues as
a separate form after death.
The soul, Aristotle defines as the first entelechy of the body. The term entelechy which sounds outlandish to us may be
replaced by the word realization or actualization and is very close in meaning to the Aristotelian use of the word form.
The soul then, according to Aristotle, is the realization or actualization or form of the body. The body takes the place of
matter in the human composite. It has the composition and the structure which give it the capacity for performing the
functions of a human being, as in any other composite, say an axe, the steel is the matter which has the potentiality or
capacity of being made into a cutting instrument. Its cutting function is the form of the axe—we might almost say the soul
of the axe, if it were not for the circumstance that it cannot do its own cutting; it must be wielded by someone else.
So far then the human soul forms an inseparable unit with the body which it informs. As we do not think of the cutting
function of an axe existing apart from the axe, so neither can we conceive of sensation, emotion or memory as existing
without a body. In so far as the soul is this it is a material form like the rest, and ceases with the dissolution of the body.
But the soul is more than this. It is also a thinking faculty. As such it is not in its essence dependent upon the body or any
corporeal organ. It comes from without, having existed before the body, and it will continue to exist after the body is no
more. That it is different from the sensitive soul is proven by the fact that the latter is inherent in the physical organ
through which it acts, being the form of the body, as we have seen. And hence when an unusually violent stimulus, say a
very bright light or a very loud sound, impinges upon the sense organ, the faculty of sight or hearing is injured to such an
extent that it cannot thereafter perceive an ordinary sight or sound. But in the rational faculty this is not the case. The
more intense the thought occupying the thinking soul, the more capable it becomes of thinking lesser thoughts. To be
sure, the reason seems to weaken in old age, but this is due to the weakening of the body with which the soul is
connected during life; the soul itself is just as active as ever.
We must, however, distinguish between two aspects of the rational soul, to one of which alone the above statements
apply. Thought differs from sensation in that the latter perceives the particular form of the individual thing, whereas the
former apprehends the essential nature of the object, that which constitutes it a member of a certain class. The sense of
sight perceives a given individual man; thought or reason understands what it is to be a member of the human species.
Reason therefore deals with pure form. In man we observe the reason gradually developing from a potential to an actual
state. The objects of the sense with the help of the faculties of sensation, memory and imagination act upon the potential
intellect of the child, which without them would forever remain a mere capacity without ever being realized. This aspect of
the reason then in man, namely, the passive aspect which receives ideas, grows and dies with the body. But there is
another aspect of the reason, the active reason which has nothing to do with the body, though it is in some manner
resident in it during the life of the latter. This it is which enables the passive intellect to become realized. For the external
objects as such are insufficient to endow the rational capacity of the individual with actual ideas, any more than a surface
can endow the sense of sight with the sensation of color when there is no light. It is the active intellect which develops
the human capacity for thinking and makes it active thought. This alone, the active intellect, is the immortal part of man.
This very imperfect sketch of Aristotle's mode of approach to the ever-living problems of God, the universe and man
shows us the wide diversity of his method from that with which the Jews of Biblical and Rabbinic tradition were identified.
Greek philosophy must have seemed a revelation to them, and we do not wonder that they became such enthusiastic
followers of the Stagirite, feeling as they must have done that his method as well as his results were calculated to enrich
their intellectual and spiritual life. Hence the current belief of an original Jewish philosophy borrowed or stolen by the
Greeks, and still betraying its traces in the Bible and Talmud was more than welcome to the enlightened spirits of the
time. And they worked this unhistorical belief to its breaking point in their Biblical exegesis.
Aristotle, however, was not their only master, though they did not know it. Plotinus in Aristotelian disguise contributed not
a little to their conception of God and his relation to the universe. The so-called "Theology of Aristotle"[25] is a Plotinian
work, and its Pantheistic point of view is in reality foreign to Aristotle's dualism. But the middle ages were not aware of
the origin of this treatise, and so they attributed it to the Stagirite philosopher and proceeded to harmonize it with the rest
of his system as they knew it.
Aristotle's system may be called theistic and dualistic; Plotinus's is pantheistic and monistic. In Aristotle matter is not
created by or derived from God, who is external to the universe. Plotinus derives everything from God, who through his
powers or activities pervades all. The different gradations of being are static in Aristotle, dynamic in Plotinus. Plotinus
assumes an absolute cause, which he calls the One and the Good. This is the highest and is at the top of the scale of
existence. It is superior to Being as well as to Thought, for the latter imply a duality whereas unity is prior to and above all
plurality. Hence we can know nothing as to the nature of the Highest. We can know only that He is, not what he is. From
this highest Being proceeds by a physical necessity, as light from a luminous body or water from an overflowing spring, a
second hypostasis or substance, the nous or Reason. This is a duality, constituting Being and Knowledge. Thus
Thought and Being hold a second place in the universe. In a similar way from Reason proceeds the third hypostasis or
the World-Soul. This stands midway between the intelligible world, of which it is the last, and the phenomenal world, of
which it is the first. The Soul has a dual aspect, the one spiritual and pertaining to the intelligible world, the other, called
Nature, residing in the lower world. This is the material world of change and decay. Matter is responsible for all change
and evil, and yet matter, too, is a product of the powers above it, and is ultimately a derivative of the Absolute Cause,
though indirectly. Matter is two-fold, intelligible and sensible. The matter of the lower world is the non-existent and the
cause of evil. Matter in a more general sense is the indeterminate, the indefinite and the potential. Matter of this nature is
found also in the intelligible world. The Reason as the second hypostasis, being an activity, passes from potentiality to
actuality, its indeterminateness being made determinate by the One or the Good. This potentiality and indeterminateness
is matter, but it is not to be confused with the other matter of the phenomenal world.
Man partakes of the intelligible, as well as of the sensible world. His body is material, and in so far forth partakes of the
evil of matter. But his soul is derived from the universal soul, and if it conducts itself properly in this world, whither it came
from without, and holds itself aloof from bodily contamination, it will return to the intelligible world where is its home.
We see here a number of ideas foreign to Aristotle, which are found first in Philo the Jew and appear later in mediæval
philosophy. Thus God as a Being absolutely unknowable, of whom negations alone are true just because he is the acme
of perfection and bears no analogy to the imperfect things of our world; matter in our world as the origin of evil, and the
existence of matter in the intelligible world—all these ideas will meet us again in Ibn Gabirol, in Ibn Daud, in Maimonides,
some in one, some in the other.
Alike in respect to Aristotle as in reference to Plotinus, the Jewish philosophers found their models in Islamic writers. The
"Theology of Aristotle" which, as we have seen, is really Plotinian rather than Aristotelian, was translated into Arabic in
the ninth century and exerted its influence on the Brethren of Purity, a Mohammedan secret order of the tenth century.
These men composed an encyclopædia of fifty-one treatises in which is combined Aristotelian logic and physics with
Neo-Platonic metaphysics and theology. In turn such Jewish writers as Ibn Gabirol, Bahya, Ibn Zaddik, Judah Halevi,
Moses and Abraham Ibn Ezra, were much indebted to the Brethren of Purity. This represents the Neo-Platonic influence
in Jewish philosophy. The Arab Aristotelians, Al Kindi, Al Farabi, Avicenna and Averroes, while in the main disciples of
the Stagirite, were none the less unable to steer clear of Neo-Platonic coloring of their master's doctrine, and they were
the teachers of the Jewish Aristotelians, Abraham Ibn Daud, Moses ben Maimon, Levi ben Gerson.
One other phase must be mentioned to complete the parallelism of Islamic and Jewish philosophy, and that is the anti-
philosophic attitude adopted by Judah Halevi and Hasdai Crescas. It was not a dogmatic and unreasoned opposition
based simply upon the un-Jewish source of the doctrines in question and their incompatibility with Jewish belief and
tradition, such as exhibited itself in the controversies that raged around the "Guide" of Maimonides. Here we have rather
a fighting of the philosophers with their own weapons. Especially do we find this to be the case in Crescas who opposes
Aristotle on philosophic grounds. In Judah Halevi similarly, though with less rigor and little technical discussion, we have
nevertheless a man trained in philosophic literature, who found the philosophic attitude unsympathetic and unsatisfying
because cold and impersonal, failing to do justice to the warm yearning after God of the religious soul. He could not
abide the philosophic exclusion from their natural theology of all that was racial and national and historic in religion,
which was to him its very heart and innermost essence.
In this attitude, too, we find an Arab prototype in the person of Al Gazali, who similarly attacked the philosophers on their
own ground and found his consolation in the asceticism and mysticism of the Sufis.
We have now spoken in a general way of the principal motives of mediæval Jewish philosophy, of the chief sources,
philosophical and dogmatic, and have classified the Jewish thinkers accordingly as Mutakallimun, Neo-Platonists and
Aristotelians. We also sketched briefly the schools of philosophy which influenced the Jewish writers and determined
their point of view as Kalamistic, Neo-Platonic or Aristotelian. There still remains as the concluding part of the
introductory chapter, and before we take up the detailed exposition of the individual philosophers, to give a brief and
compendious characterization of the content of mediæval Jewish philosophy. We shall start with the theory of
knowledge.
We have already referred to the attitude generally adopted by the mediæval Jewish thinkers on the relation between
religion and philosophy. With the exception of Judah Halevi and Hasdai Crescas the commonly accepted view was that
philosophy and religion were at bottom identical in content, though their methods were different; philosophy taught by
means of rational demonstration, religion by dogmatic assertion based upon divine revelation. So far as the actual
philosophical views of an Aristotle were concerned, they might be erroneous in some of their details, as was indeed the
case in respect to the origin of the world and the question of Providence. But apart from his errors he was an important
guide, and philosophy generally is an indispensable adjunct to religious belief because it makes the latter intelligent. It
explains the why's and the wherefore's of religious traditions and dogmas. Into detailed discussions concerning the origin
of our knowledge they did not as a rule go. These strictly scientific questions did not concern, except in a very general
way, the main object of their philosophizing, which was to gain true knowledge of God and his attributes and his relation
to man. Accordingly we find for the most part a simple classification of the sources of knowledge or truth as consisting of
the senses and the reason. The latter contains some truths which may be called innate or immediate, such as require no
experience for their recognition, like the logical laws of thought, and truths which are the result of inference from a fact of
sensation or an immediate truth of the mind. To these human sources was added tradition or the testimony of the
revealed word of God in the written and oral law.
When Aristotle began to be studied in his larger treatises and the details of the psychology and the metaphysics became
known especially through Averroes, we find among the Jews also an interest in the finer points of the problem of
knowledge. The motives of Plato's idealism and Aristotle's conceptualism (if this inexact description may be allowed for
want of a more precise term) are discussed with fulness and detail by Levi ben Gerson. He realizes the difficulty involved
in the problem. Knowledge must be of the real and the permanent. But the particular is not permanent, and the universal,
which is permanent, is not real. Hence either there is no knowledge or there is a reality corresponding to the universal
concept. This latter was the view adopted by Plato. Gersonides finds the reality in the thoughts of the Active Intellect,
agreeing in this with the views of Philo and Augustine, substituting only the Active Intellect for their Logos. Maimonides
does not discuss the question, but it is clear from a casual statement that like Aristotle he does not believe in the
independent reality of the universal (Guide III, 18).
In theoretical physics the Arabian Mutakallimun, we have seen (p. xxii), laid great stress on the theory of atom and
accident as opposed to the concepts of matter and form by which Aristotle was led to believe in the eternity of the world.
Accordingly every Mutakallim laid down his physical theory and based on it his proof of creation. This method was
followed also by the early Jewish thinkers. The Karaites before Maimonides adopted the atomic theory without question.
And Aaron ben Elijah, who had Maimonides's "Guide" before him, was nevertheless sufficiently loyal to his Karaite
predecessors to