The following is an outline of his dogmas, so far as is necessary for our purpose:
“All bodies beneath the firmament are compounded of matter and form.”[[90]] But “form” here is not “form as vulgarly understood, which is the picture and image of the thing”; it is “the natural form,” that is to say, the reality of the thing, “that by virtue of which it is what it is,” as distinct from other things which are not of its kind.[[91]]
“Matter is never perceived without form, nor form without matter; it is man who divides existing bodies in his consciousness, and knows that they are compounded of matter and form.”[[92]] For since the form is the reality, by virtue of which the thing is what it is, it follows that matter without form would be a thing without a real existence of its own: in other words, a mere intellectual abstraction. And it is superfluous to add that form without matter does not exist in the sublunar world, which consists wholly of “bodies.”[[93]]
“The nature of matter is that form cannot persist in it, but it continually divests itself of one form and takes on another.” It is because of this property of matter that things come into being and cease to be, whereas form by its nature does not desire change, and ceases to be only “on account of its connection with matter.” Hence “generic forms are all constant,” though they exist in individuals which change, which come and go; but individual forms necessarily perish, since their existence is possible only in combination with finite matter.[[94]]
“The soul of all flesh is its form,” and the body is the matter in which this form clothes itself. “When, therefore, the body, which is compounded of the elements, is dissolved, the soul perishes, because it exists only with the body” and has no permanent existence except generically, like other forms.[[95]]
“The soul is one, but it has many different faculties,” and therefore philosophers speak of parts of the soul. “By this they do not mean that it is divisible as bodies are; they merely enumerate its different faculties.” The parts of the soul, in this sense, are five: the nutritive, the sensitive, the imaginative, the emotional, and the rational. The first four parts are common to man and to other animals, though “each kind of animal has a particular soul” special to itself, which functions in it in a particular way, so that, for instance, the emotion of a man is not like the emotion of an ass. But the essential superiority of the soul of man lies in its possession of the additional fifth part—the rational: this is “that power in man by which he thinks and acquires knowledge and distinguishes between wrong actions and right.”[[96]]
Thus the soul of man differs from the souls of other living things only in the greater variety and higher quality of its functions. In essence it is, like “the soul of all flesh,” simply a form associated with matter, having no existence apart from the body. When the body is resolved into its elements the soul also perishes with all its parts, including the rational.
This extreme conclusion had already been deduced from the teaching of Aristotle by some of his early commentators (such as Alexander Aphrodisius). There were, indeed, other commentators who, unable to abandon belief in the survival of the soul, tried to explain Aristotle’s words in conformity with that belief by excluding the rational part from the “natural form” and attributing to it a separate and eternal existence.[[97]] But Maimonides was too logical not to see the inconsistency involved in that interpretation; and so he sided with the extremists, though their view was absolutely opposed to that belief in personal immortality which in his day had come to be generally accepted by Jews. Had he been content with that view alone, he would inevitably have gone back to the conception of primitive Judaism, as we find it in the Pentateuch: that immortality belongs not to the individual, but to the nation; that the national form persists for ever, like the generic form in living things, and the changing individuals are its matter. In that case his whole ethical system would have been very different from what it is. But Maimonides supplemented the teaching of Aristotle by another idea, which he took from the Arabs; and this idea, amplified and completed, he made the basis of his ethical system, which thereby acquired a new and original character, distinguished by its fusion of the social and the individual elements.
The idea is in substance this: that while reason, which is present in a human being from birth, is only one of the faculties of the soul, which is a unity of all its parts and ceases wholly to exist when the body ceases, yet this faculty is no more than a “potential faculty,” by virtue of which its possessor is able to apprehend ideas; and therefore its cessation is inevitable only if it remains throughout its existence in its original condition—in the condition, that is, of a “potential faculty” whose potentiality has not been realised. But if a human being makes use of this faculty and attains to the actual apprehension of Ideas, then his intellect has proceeded from the stage of potentiality to that of actuality: it has achieved real existence, which is permanent and indestructible, like the existence of those Ideas which it has absorbed into itself and with which it has become one. Thus we are to distinguish between the “potential intellect,” which is given to a human being when he comes into the world, and is merely a function of the body, and the “acquired intellect,” which a human being wins for himself by apprehending the Ideas. This acquired intellect “is not a function of the body and is really separate from the body.” Hence it does not cease to exist with the cessation of the body; it persists for ever, like the other “separate Intelligences.”[[98]]
Now since the form of every existing thing is that individual essence by virtue of which it is what it is and is distinguished from all other existing things, it is clear that the acquired intellect, which gives its possessor immortality, is the essence of the human being who has been privileged to acquire it: in other words, his true form, by which he is distinguished from the rest of mankind. In other men the form is the transient soul given to them at birth; but in him who has the acquired intellect even the soul itself is only a kind of matter. His essential form is “the higher knowledge,” “the form of the soul,” which he has won for himself by assimilating “Ideas which are separate from matter.”[[99]]