There are differences of opinion among philosophers about the kinds of material and immaterial substances. The Peripatetics divided substances into five types:
1. Intellectual substances are completely immaterial, and in addition to having no spatial or temporal dimensions by nature, they are not attached to any material or corporeal existents.
It must be noted that the application of ‘intellect’ to such existents is unrelated to intellect in the sense of the power which perceives universal concepts, and the employment of the term ‘intellect’ regarding completely immaterial substances is a sort of homonymity, as is the employment of ‘intellect’ by scholars of ethics in yet a third sense.
2. Psychic substances are essentially immaterial, but are attached to bodies (corporeal existents), and without a body they have no possibility of coming about, although it is possible that after coming about their attachment to a body may be cut off, and after the death of the body they may persist.
3. Corporeal substances have spatial and temporal dimensions, and we sense their appearances in the form of accidents of color and shape, while we prove their existences by reason. The Peripatetics considered every corporeal substance to be composed of two other substances by the name of ‘matter’ and ‘form.’
4. Matter or hayula is also an indefinite substance without actuality according to the Peripatetics. It exists in all bodies, including the celestial spheres and the elements. However, the matter of each celestial sphere takes its own specific form, and for this reason, as they speculated, generation and corruption, and tearing and mending are impossible for them.
However, elemental matter takes different kinds of forms (except for that of the celestial spheres), and in this regard the world of elements is the world of alterations and transformations, of generation and corruption.
5. Form is the aspect of actuality for every corporeal existent and is the source of the particular effects of every kind of matter. There are various kinds of forms, and among them is the form of corporeality which exists in all corporeal substances and is inseparable from hayula.
There are other forms which also occur successively concomitant with the form of corporeality in the different types of corporeal things and are capable of change, transformation, generation and corruption, such as the elemental forms, mineral forms, vegetable forms and animal forms.
On the other hand, Shaykh al-Ishraq denied the existence of hayula as a substance without actuality as a part of corporeal substance. He took the form of corporeality to be the corporeal substance itself and he accepted other elemental, mineral and vegetable forms as accidents of corporeal substance.
Of the five kinds of substances posited by the Peripatetics, he accepted only three (intellectual substance, psychic substance and corporeal substance), but he also attested to another kind of existent as an intermediary between the completely immaterial and the purely material by the name of ‘immaterial phantoms’ (ashbah mujarradah) or ‘suspended forms’ (suwar mu’allaqah) which he later introduced in the terminology of more recent philosophers as ‘imaginal’ (mithali) or ‘intermediary’ (barzakhi) substance.
Earlier it was mentioned that Berkeley denied the existence of corporeal substances and consequently, matter and material forms. He believed that what we perceive as material things are really forms which God the Exalted has brought into existence in our psychic world, and that their realities are psychic realities, and that there exists no material world beyond the soul.
It was also mentioned that Hume also considered psychic substance to be doubtful and announced that we can only decisively prove psychic phenomena (accidents), for these are the only things which can be directly experienced.
In Lesson Twenty-Three we proved the existence of a material reality, and it was explained that it is incorrect to imagine that the material world exists only in the psychic world and in the realm of man’s perception, for by means of presentational knowledge man finds that he does not bring sensible forms into existence himself.
Hence, there is no other alternative but that they are brought about by a cause external to him which somehow influences his sensory perceptions. The hypothesis that God the Exalted made these perceptual forms to appear in our souls without intermediary—as was held by Berkeley—is also an incorrect assumption, because the relations between an immaterial agent and all souls and all times and places are equal.
Hence, the appearance of specific phenomena at a definite time without the mediation of preparatory agents and specific temporal and spatial conditions cannot take place, although the entire world of being is the creation of God the Exalted, and He is the only one who gives being to existents, as will be explained in the proper place.
Moreover, with the denial of the existence of matter, no room remains for the soul as a substance attached to matter, and it would have to be considered an intellectual substance and a completely immaterial thing, while completely immaterial things cannot be the objects of accidents or of alterations.
It is to be concluded that the belief in a material world, in addition to being spontaneous (irtikazi) and in a sense ‘innate’ (fitri), is also necessitated by rational proof. In this regard, some Western thinkers have proclaimed that what is provable about the material world is only those accidents which may be the objects of sense experience, and that corporeal substance is not provable.
For example, when an apple is the object of sense perception, by means of the eyes we see its color and shape, we smell its fragrance, by touching it we perceive its smoothness, and by eating it, its taste, but there is no sense by which we perceive that there is something called the substance of apple, the locus of its accidents, in addition to the color, shape, smell, taste and things like that.
In retort to them it must be said that although we do not have a sense for perceiving substance, by reason itself we understand that objective existents are either accidents or substances, where by accident is meant a state or attribute for something else, something that needs a subject to which the attribute applies, while a substance is something which does not need an objective subject of attribution.
Hence, if that which relates to sense perceptions is an accident, inevitably it will be in need of a substantial subject, and if it does not need a subject, then it itself will be a substance. In any case, there is no rational alternative to accepting the existence of material substance. However, it is another matter to identify objective substances and accidents which we presently have no intention to investigate.
In Lesson Thirteen we mentioned that presentational knowledge of the soul is the same as the existence of the soul itself, and that every human being possesses this knowledge to a greater or lesser extent. But this knowledge has degrees, and at the beginning a weak level occurs, which correlates with the weakness of the existence of the soul. For this reason, it is not an object of awareness.
Gradually, a weak awareness of it appears, but not to the extent that a clear mental interpretation of it may be formed. For this reason it is confused with the body. The more the existence of the soul is perfected, and the level of its immateriality is raised, the more its awareness of itself will be increased until it reaches the point that it becomes clear that it is an immaterial substance which is independent of the body.
However, such knowledge will be obtained by none but those who advance through levels of spiritual perfection. Therefore, the majority of people are in need of proof to obtain conscious knowledge of the immateriality of the soul.
There are various ways to prove the immateriality of the soul, the examination of which merits an independent book of its own. Among them there are reasons given from dreams, the summoning of spirits, hypnotism, and likewise from the works of yogis, miracles of the friends of God (awliya), and such things. Some of their premises are established by reports for those who do not have direct information of such things, and in truth these sorts of reports are corroborated way beyond what is required for credibility.
Another group of reasons makes use of premises which must be proven in the empirical sciences, especially psychology and biology, such as the premise that all organs and cells of the body are gradually replaced, and even the cells of the brain are altered as a result of dissolution and nourishment with fresh material, while the soul has a fixed individual existence which survives through dozens of years, and every man is aware of his own individual identity.
Purely philosophical arguments for the immateriality of the soul are also divided into two groups: one group of arguments are those which are obtained by the analysis of ordinary knowledge by presence; the other group of arguments first establish the immateriality of psychic phenomena such as perception, will and affection, then they prove the immateriality of their subject, the soul.
Since we will discuss the immateriality of the qualities of the soul in the future, especially the immateriality of knowledge and perception, here we will content ourselves with some arguments which directly establish the immateriality of the soul.
1. Ibn Sina, in his Isharat, presents an argument for the immateriality of the soul that may be summarized as follows.
If one is placed in an environment in which his attention is not distracted by external things, and the condition of his body is such that he does not notice it, that is, he does not suffer from hunger, thirst, cold, heat, pain or any other discomfort, and even the weather is completely still so that the blowing of the wind does not attract his attention, and in the words of Ibn Sina, there is ‘balmy weather,’ in such a situation if one focuses one’s attention on oneself, that is, on the ‘I, the perceiver,’ so that one has no attention on anything corporal, he will find his soul, while he will not find any of his bodily organs. What he finds is different from what he does not find, and hence the soul is other than the material body.
This argument, as we have considered it, is an aid to enable the mind to have a correct interpretation of presentational knowledge of the soul. The conditions mentioned by Ibn Sina are really a guide for the common man to be able to focus his attention so that material factors do not attract his attention to the body and things related to it.
It was previously indicated that those who are advanced in the stages of spiritual perfection are able to turn their own attention completely toward the soul and to observe the reality of it, but the common man must observe such conditions in order to divert his attention from material things to some extent.
2. Another argument for the immateriality of the soul is that when we pay precise attention to our own existence, the ‘I, the perceiver,’ we see that the existence of ‘I’ is a simple indivisible thing. For example, it cannot be divided into two ‘half I’s,’ while the most fundamental characteristic of body is divisibility, as was explained in Lesson Forty-One. However, such a characteristic cannot be found in the soul, and it is not subject to the body in being divisible.
So, there is no other alternative but its immateriality. The most that can be said is that the soul is attached to the body and has a special existential relation to it, so that it influences the body, as the body moves with the will of the soul, and it is affected by the body, as it suffers hunger and thirst and is influenced by and influences the body in many other ways that must be taken up in discussions of the mind- body problem.