To refute their claim that nothing can share with the First its genus, and be diferentiated from it through a specific diference,  and that with respect to its intellect the division into genus and specific difference cannot be applied to it,

Ghazali says:

Indeed, they are all of this opinion, and they deduce from this that, since nothing can share its genus, it cannot be differentiated through a specific difference and cannot have a definition, since a definition is constructed out of genus and specific difference and what has no composition cannot have a definition, for a definition is a kind of composition. ‘ And they affirm that, since the First is said to resemble the first effect in being an existent and a substance and a cause for other things, and to differ from it in other respects, this certainly does not imply sharing in its genus; no, it is nothing but a sharing in a common necessary attribute. The difference between genus and necessary attribute consists in their content, not in universality, according to logical theory, for the genus, namely, the essential universal, is the answer to the question what the thing is, and is subsumed under the quiddity of the thing defined, and constitutes its essence: a man’s being alive is subsumed under the quiddity of man, i. e. his animality, and is his genus, but his being born and created are his necessary attributes, and, although they are universals which can never be separated from him, are not subsumed under his quiddity, according to logical theory, about which there can be no misgiving. ; And the philosophers affirm that existence is never subsumed under the quiddity of things, but stands in a relation to the quiddity, either necessarily and inseparably, like its relation to heaven, or subsequently, after their nonexistence, like its relation to temporary things, and that the sharing of existence does not imply a sharing in genus. And as to its sharing in ‘being a cause to other things’ with all the other causes, this is a necessary relation which likewise cannot be subsumed under the quiddity, s for neither the fact of being a principle nor existence constitutes the essence, but they are necessary attributes of the essence, consequent upon the constitution of the essence out of the parts of its quiddity, and this community is only the sharing of a necessary common attribute consecutive to the essence, not a community of genus. Things therefore are only defined by their constituents, and if they are defined by the necessary attributes this is only a description’ to differentiate them, not to define their essential forms; for the triangle is not defined by the fact that its angles are equal to two right angles, although this is a necessary and common attribute of all triangles, but it is defined as a figure bounded by three sides. And the same applies to its being a substance, and the meaning of its being a substance is that it is an existent which does not exist in a substratum. ‘ And the existent is not a genus, since, as it is related to a negation, namely not being in a substratum, it cannot become a constituent genus; indeed, even if it could be brought into a relation to something positive and it could be said that it existed in a substratum, it could not become a genus in the accident. And the reason is that the man who knows substance by its definition, which is rather its description, namely that it is an existent which does not exist in a substratum, does not know whether it exists, and a fortiori does not know whether it exists in a substratum or not; no, the meaning of the description of substance is that it is the existent which does not exist in a substratum, i. e. that it is a certain reality which, when it does exist, does not exist in a substratum, but we do not mean that it actually exists at the time of the definition, and its community is not the community of the genus, for only the constituents of the quiddity form the community of the genus which needs also a specific differences But the First has no other quiddity, except necessary existence, and necessary existence is its real nature and its own quiddity, exclusively confined to it, and since necessary existence is exclusively confined to the First, it cannot be shared by others, it cannot have a specific difference, and it cannot have a definition.

I say:

Here ends what Ghazali says of the philosophical views about this question, and it is partly true, partly false. As to his statement that no other thing can share with the First its genus and be distinguished from it through a specific difference, if he means by this the genus and the difference that are predicated univocally, it is true, for anything of this description is composed of a common form and a specific form, and such things possess a definition. But if by ‘genus’ is meant what is predicated analogically, I mean pier prius et piosterius, then it can have a genus, e. g. existent, or thing, or identity, or essence, and it can have a kind of definition, and this kind of definition is used in the sciences-for instance, when it is said of the soul that it is the entelechy of the natural organic body, a and when it is said of the substance that it is the existent which does not exist in a substratum -but these definitions do not suffice for knowledge of the thing, and they are only given to indicate through it the different individuals which fall under such definitions and to represent their peculiarities. But as to his statement that according to the philosophers the term ‘existence’ only indicates a necessary attribute of the essences of things, this is not true, and we have already explained this in another place and none of the philosophers has said this but Avicenna. Having denied that existence is a genus, predicted either univocally or equivocally, Avicenna affirmed that it was a term which signified a common necessary attribute of things. But the difficulty he found in regarding existence as an essence can be held up against him when it is regarded as a necessary attribute, for if it were a necessary attribute, this necessary attribute could not be given as an answer to the question what a thing is. I And further, if ‘existence’ really signifies a necessary attribute in things, does it signify this necessary attribute univocally, or equivocally, or in some other mode of attribution? And if it has a univocal meaning, how can there be an accident univocally predicated of things essentially different (I believe that Avicenna regarded this as possible)? z It is, however, impossible, because from different things the congruous and identical can only derive, when these different things agree in one nature, since necessarily a single necessary attribute must come from one nature, just as a single act can proceed only from one nature. And since this is impossible, the term ‘existence’ indicates essences which have analogical meanings, essences some of which are more perfect than others; and therefore there exists in the things which have such an existence a principle which is the cause of that which exists in all the other things of this genus, just as our term ‘warm’ is a term which is predicated per prius et posterius of fire and all other warm things, and that of which it is asserted first, i. e. fire, is the cause of the existence of warmth in all other things, and the same is the case with substance, intellect, and principle and such terms (most metaphysical terms are of this kind), and such terms can indicate both substances and accidents.

And what he says of the description of substance is devoid of sense, but existence is the genus of substance and is included in its definition in the way the genera of the sublunary things are included in their definitions, and Farabi proved this in his book about demonstration, and this is the commonest view amongst philosophers. Avicenna erred in this only because, since he thought that the ‘existent’ means the ‘true’ in the Arabic language, and that what indicates the true indicates an accident4-the true, however, really indicates one of the second, predicates, i. e. a predicable-he believed that when the translator used the word ‘existent’ it meant only the ‘true’. This, however, is not so, for the translators meant only to indicate what is also meant by ‘entity’ and ‘thing’. Farabi explains this in his Book of the Letters and he shows that one of the reasons for the occurrence of this mistake is that the term ‘existent’ in Arabic is a derivative in form and that a derivative signifies an accident, and in fact an accident is linguistically a derivative. But since the translators did not find in Arabic a term which signified that concept which the ancient philosophers subdivided into substance and accident, potency and act, a term namely which should be a primitive symbol, some translators signified that concept by the term ‘existent’, not to be understood as having a derivative meaning and signifying therefore an accident, but as having the same meaning as ‘essence’. It is thus a technical term, not an idiomatic word. Some translators, because of the difficulty attached to it, decided to use for the concept, which the Greek language tried to express by deriving it from the pronoun which joins the predicate and the subject, the term which expresses this, because they thought that this word comes nearer to expressing this meaning, and they used instead of the term ‘existent’ the term ‘haeceitas’, but the fact that its grammatical form is not found in Arabic hindered its use, and the other party therefore preferred the term ‘existent’. -, And the term ‘existent’ which signifies the true does not signify the quiddity, and therefore one may often know the quiddity without knowing the existence, and this meaning of ‘existent’ of necessity does not signify the quiddity in the compound substance, but is in the simple substance identical with the quiddity; and this meaning is not what the translators intended by ‘existence’, for they meant the quiddity itself, and when we say of the existent that it is in part substance, in part accident, the sense meant by the translators must be understood, and this is the sense which is predicated analogically of different essences of things. When we say, however, that substance exists, it must be understood in the sense of the true. And therefore if we have understood the well-known discussion of the ancient philosophers, whether the existent is one or more than one, which is found in the first book of Aristotle’s Physics where he conducts a discussion with the ancient philosophers Parmenides and Melissus, s we need only understand by ‘existent’ that which signifies the essence. And if the ‘existent’ meant an accident in a substratum, then the statement that the existent was one would be self-contradictory. ‘ And all this is clear for the man who is well grounded in the books of the philosophers.

And having stated the views of the philosophers, Ghazali begins to refute them, and says:

This is the sense of the doctrine of the philosophers. And the discussion with them consists of two parts: a question and a refutation. The question is: This is the simple narration of your doctrine, but how do you know the impossibility of this with respect to God, so as to build on it the refutation of dualism, since you say that a second God would have to participate in something and differ from the first in something, and that which partly possesses something in common with another, partly is different from it, is compound, whereas that He should be compound is absurd?

I say:

I have already said that this is only valid for something which possesses a common feature through a genus which is predicated univocally, not analogically. For if, by the assumption of a second God, a God were assumed of the same rank of divinity as the first, then the name of God would be predicated univocally, and He would be a genus, and the two Gods would have to be separated by a specific distinction and both would be compounded of a genus and a specific distinction, and the philosophers do not allow a genus to an eternal being; but if the term ‘existence’ is predicated per prius et posterius, the prior will be the cause of the posterior.

Ghazali says, refuting the philosophers:

But we say: How do you know the impossibility of this kind of composition? For there is no proof except your denial of the attributes, which has been mentioned, namely that the compound of genus and species is an aggregate of parts; thus if it is possible for one or for a collection of the parts to exist without the others, this single one will be the necessary existent and the others will not be necessary; and if it is possible neither for the parts to exist without the totality, nor for the totality to exist without the parts, then the whole is an effect needing something else as its cause. We have already discussed this in the case of the attributes, and have shown that their plurality is not impossible, since an end of the causal series is admitted and all that is proved is that there is an end of the causal series. For those enormous difficulties which the philosophers have invented concerning the inherence of attributes in the necessary existent there is no proof whatever. If the necessary existent is what the philosophers describe it to be, namely to possess no plurality and not to need anything else for its existence, then there is no proof of the existence of this necessary existent; the only thing proved is that there is an end of the causal series, and we have exhausted this subject in our discussion of attributes. And for this kind of plurality it is still more obvious, for the division of a thing into genus and specific difference is not like the division of the subject into essence and attribute, since, indeed, the attribute is not the essence and the essence is not the attribute, but the species is not in every way different from the genus, for whenever we mention the species, we mention the genus with an addition, and when we speak of a man we only mention animal with the addition of reason. ‘ And to ask whether humanity can be free from animality is like asking whether humanity can be without itself, when something is added to it. And indeed genus and species are more distant from plurality than attribute and subject. ‘ And why should it be impossible that the causal series should end in two causes, one the cause of the heavens and the other the cause of the elements, or one the cause of the intellects and the other the cause of all bodies, and that there should be between those two causes a conceptual difference and separation as between redness and warmth when they exist in one and the same place? For they differ in content without our being obliged to assume in the redness a compound of genus and specific difference through which this difference is established; indeed, if it possesses a plurality, this kind of plurality does not impair the singleness of its essence, and why should this be impossible with respect to the causes? Through this there is shown the weakness of their refutation of the existence of two Gods.

I say:

Composition out of genus and specific difference is exactly the same as the composition of a thing in potency and a thing in act, for the nature which is indicated by the genus does not actually exist at any time without the presence of the nature which is called specific difference and form. ; And everything which is composed of these two natures is, according to the philosophers, transitory, and possesses an agent, for the specific difference is one of the conditions for the existence of the genus in so far as the genus is in potency and does not exist without the specific difference. And the conjunction of either with its partner is in a certain way a condition for the existence of the other. And as a thing cannot itself be a cause of the condition of its existence, it necessarily possesses a cause which provides it with existence by conjoining the condition and the conditioned. Also, according to the philosophers the recipient is in reality something which possesses only potency, and if it is actually, then only accidentally; and what is received is actuality, and if it is potency, then only accidentally; for the recipient and the thing it receives are only distinguished by the fact that one of them is potentially something else, whereas actually it is the thing received and whatever is potentially another thing must necessarily receive this other thing and lose the thing it actually is. ‘ Therefore, if there should exist a recipient in actuality and a thing received in actuality, both would exist by themselves, but the recipient is necessarily body, for only body, or what is in a body, possesses receptivity primarily, and receptivity cannot be attributed to accidents and forms, nor to the plane, the line, and the point, ‘ nor in general to what cannot be divided. As regards an incorporeal agent, this has been already proved, and as to an incorporeal recipient, or a recipient not embedded in matter, such a recipient is impossible, although there is a problem for the philosophers about the potential intellects And indeed, if the compound has a subject and an attribute which is not additional to its essence, b it is transitory and necessarily a body, and if it has a subject and an attribute additional to its essence, without its having any potency in its substance even in respect of this attribute, as is the case according to the ancients with the body of the heavens, ? it possesses quantity of necessity and is a body. For, if from such an essence, supporting the attribute, bodiliness were taken away, it would no longer be a perceptible recipient, and equally the sensory perception of its attribute would be annulled and its attribute and subject would both become intellect, and they would be reduced to one single simple entity, for from the nature of the intellect and the intelligible it is evident that they are both one and the same thing, since plurality exists in them accidentally, namely through the substratum. ‘ And in short, when the philosophers assume an essence and attributes additional to the essence, this amounts to their assuming an eternal body with accidents inherent in it, and they do not doubt that if they took away the quantity which is corporeity, the perceptible element in it would be annulled, and neither substratum nor inherent would exist any more; but if, on the other hand, they regarded the substratum and the inherent as abstracted from matter and body, the substratum and inherent would of necessity be both intellect and intelligible; but this is the Unique, the Uncompounded, God, the Truth.

As to his statement that the whole mistake of the philosophers consists in their calling the First the ‘necessary existent’, and that if instead they called it ‘the causeless”, the conclusion which they draw about the First, concerning the necessary attributes of the necessary existent, would not follow-this statement is not true. For since they assume an existent which has no cause, it follows necessarily that it is in itself a necessary existent, just as, when a necessary existent existing by itself is assumed, it follows necessarily that it has no cause, and if it has no cause it is more appropriate that it should not be divided into two things, cause and effect. The assumption of the theologians that the First is composed of an attribute and a subject implies that it has an efficient cause, ‘ and that therefore it is neither a first cause nor a necessary existent, and this is in contradiction to their assumption that it is one of those existents of which the attribute and the subject are reduced to one single simple entity; but there is no sense in repeating this and expatiating on it.

And as to his statement that it is not impossible of God, the First, that He should be composed of a substratum and an attribute additional to the substratum, and that therefore a fortiori it is not impossible that He should be composed of a substratum and an attribute which is identical with its substratum, we have already explained the way in which this is not impossible, namely when both are abstract from matter.

And as to his statement that their refutation of dualism does not prevent the possibility of the existence of two Gods, one of whom would be, for instance, the cause of heaven and the other the cause of the earth, or one the cause of the intelligible and the other the cause of the sensible in the bodies, and that their differentiation and distinction need not determine a contradiction, as there is no contradiction in redness and warmth which exist in one place-this statement is not true. For if the production and creation of the existent is assumed to be the effect of one nature and of one essence, not of two different natures, it would necessarily follow that if a second thing of this nature were assumed, similar in nature and intellect to the first, they would share in one attribute and differ in another. And their difference would come about either through the kind of differentiation which exists between individuals or through the kind of differentiation which exists between species. In the latter case the term ‘God’ would be predicated of them equivocally, and this is in contradiction with their assumption, for the species which participate in the genus are either contraries or stand between contraries, and this is wholly impossible. And if they were individually differentiated, they would both be in matter, and this is in opposition to what is agreed about them. But if it is assumed that one of these natures is superior to the other and that this nature is predicated of them per prius et posterius, then the first nature will be superior to the second and the second will be necessarily its effect, so that for instance the creator of heaven will be the creator of the cause which creates the elements; and this is the theory of the philosophers. And both theories lead to the acceptance of a first cause; that of those who believe that the First acts through the mediation of many causes, and that of those who believe that the First is directly the cause of all other things without mediation. But according to the philosophers this latter theory cannot be true. For it is evident that the worlds exist through cause and effect, and it is inquiry concerning these causes which leads us to a first cause for everything. And if some of these different principles were wholly independent of others-that is, if some were not the cause of others-then the world could not be a single well connected whole, and to the impossibility of this the Divine Words refer, ‘Were there in both heaven and earth Gods beside God, both surely would have been corrupted’.

Ghazali says:

It may be said: This is impossible so far as the difference which exists between these two essences is either a condition for their necessary existence (and in that case it will exist in both the necessary existents, and then they will not differ anyhow), or neither the one nor the other specific difference is a condition (and since the necessary existence is able to exist without the things that are not a condition for it, the necessary existence will be perfected by something else).

But we reply: This is exactly the same answer as you gave concerning the attributes and we have already discussed it, ‘ and the source of confusion throughout this problem is the expression ‘necessary existent’; let us therefore get rid of this term; and indeed, we do not accept that demonstration proves a necessary existent, if anything else is meant by it but an eternal existent which has no cause, and if this is meant by it, let us abandon the term ‘necessary existent’ and let it be proved that an existent which has no cause and no agents cannot have a plurality and a distinctive mark, but indeed there is no proof of it. There remains therefore your question whether this specific difference is a condition of the causeless character of this causeless existent, and this is nonsense. For we have shown that there is no cause for its being without a cause, so as to make it possible to ask for its condition. It would be like asking whether blackness is a condition for the colour’s becoming a colour, and if it is a condition, why redness is then a colour. And the answer is: as to the essential nature of colour, i. e. in so far as the essence of colouredness is asserted in the intellect, neither of them is a condition, < and as to its existence, each of them is a condition for its existence, but not individually, since a genus cannot exist in reality without a specific differences And likewise the man who accepts two causes as starting-points of the series must say that they are differentiated through a specific difference, and both differences are a condition for their existence, no doubt, though not through their individuality.

I say:

The summary of what he says here of the proof of the philosophers is that they say that the specific difference through which the duality in the necessary existent occurs is either a condition or not a condition for necessary existence. If the specific difference through which they are distinguished is a condition for both the necessary existents, they will no longer be separated in their necessary existence and the necessary existent will be of necessity one and the same, just as, if black were to be a condition for the necessity of colour and white a condition for colouredness, they could not differ in colouredness. If, on the other hand, the specific difference does not enter into the essence of necessary existence, then both these necessary existents will have necessary existence only by accident, and their duality will not be based on their both being necessary existents. This, however, is not true, for the species are a condition for the existence of the genus, and both colours are a condition for the existence of the genus, though not individually (for in this case they could not exist together in the existence of the colour).

Ghazali opposes this statement with two arguments. The first is that this can only happen in so far as ‘necessary existent’ means a special nature; according to the theologians, however, this is not the case, for they understand by ‘necessary existent’ only something negative, namely something which has no cause, and since negative things are not caused, how can, for the denial of the causeless, an argument like the following be used: ‘That which distinguishes one causeless entity from another causeless entity is either a condition of its being causeless or not; if it is a condition, there cannot be any plurality or differentiation; and if it is not a condition, it cannot occasion a plurality in the causeless, which therefore will be one. ‘ However, the erroneous part in Ghazali’s reasoning is that he regards the causeless as a mere negation, and, as a negation has no cause, he asks how it could possess a condition which is the cause of its existence. But this is a fallacy, for particular negations, which are like infinite terms and which are used for distinguishing between existents, , have causes and conditions which determine this negation in them, just as they have causes and conditions which determine their positive qualities; and in this sense there is no difference between positive and negative attributes, and the necessity of the necessary existent is a necessary attribute of the causeless and there is no difference between saying ‘the necessary existent’ or ‘the causeless’.

And the nonsense comes from those who talk like Ghazali, not from his opponents.

And the summary of Ghazali’s second objection is that to say, as the philosophers do, that the specific difference through which the necessary existent is distinguished is either a condition or not, that in the former case the one necessary existent cannot be distinguished from the other in so far as they are necessarily existent and that therefore the necessary existent is one, and that in the latter case the necessary existent has no specific difference through which it can be divided: that to speak like this is like saying that if there exist more colours than one of the genus colour, the difference through which one colour is distinguished from another is either a condition for the existence of colour or not; that in the former case the one cannot be distinguished from the other in so far as they are colour, and colour is therefore one single nature; that in the latter case, if neither of them is a condition for the existence of colouredness, one colour has no specific difference through which it can be distinguished from another, and this is not true. ‘

Ghazali says, answering this problem on behalf of the philosophers:

It may be said perhaps: This is possible in the case of colour, for it has an existence related to the quiddity and additional to the quiddity, but it is not possible for the necessary existent, for it possesses only necessary existence, and there is therefore no quiddity to which its existence might be related, and just as the specific differences of black and red are not conditions for colouredness being colouredness, but only a condition for the actual realization of colour through a cause, , in the same way the specific difference cannot be a condition for necessary existence, for necessary existence is in relation to the First what colouredness is in relation to the colour, and not like the existence brought in relation to colouredness.

But we reply, we do not accept this; on the contrary, the necessary existent has a real essence to which existence is attributed, as we shall show in the next discussion, and their statement that the First is an existence without quiddity is incomprehensible. The trend of their argument is, in short, that they base their denial of dualism on the denial that the First is composed of the generic and the specific, then they base the denial of this on their denial that there is a quiddity behind the existence. Therefore as soon as we have refuted this last proposition, which is their fundamental principle, their whole structure (which is a very shaky fabrication, just like a spider’s web) tumbles down.

I say:

Ghazali builds the answer he gives here in the name of the philosophers on their statement that existence is an accident in the existent, i. e. the quiddity, and he objects against them that the existence in everything is something different from the essence, and he affirms that their whole argument is built only on this. ‘ But the distinction which the philosophers make here does not save them from the implication held against them about colouredness and its specific differences, in whatever way they may turn the question. Indeed, nobody doubts that the specific differences of the genus are the cause of the genus, whether it is assumed that the existence of the genus is different from its essence, or that the essence and existence of the genus are identical; for if the specific differences were differences in the existence, and the existence of the colour were different from the quiddity of the colour, it would follow that the specific differences by which the colour is divided are not differences in the quiddity of the colour, but differences in one of its accidents, and this is an absurd assumption. Therefore the truth is to say, ‘When we divide colour by its specific differences, the existence of the colour in so far as it is colour is only actual, either because it is white, or because it is black or any other colour. Thus we do not divide an accident of the colour, but we divide only the essence of the colour. Through this solution the statement that existence is an accident in the existent is seen to be false, and the argument and his answer arc unsound.

As to Ghazali’s words:

They base their denial of dualism on the denial that the First is composed of the generic and the specific, then they base the denial of this on the denial that there is a quiddity behind the existence. Therefore as soon as we have refuted this last proposition, which is their fundamental principle, their whole structure tumbles down.

I say:

This argument is not sound, for their structure, the denial of individual duality attributed to simple things univocally, is self-evident, for if we assume a duality and two simple things possessing a common trait, the simple becomes a compounds And the summary of the philosophical proof for this is that the nature called ‘necessary existent’, i. e. the cause which has no cause and which is a cause for other things, must be either numerically one or many; if many, it must be many through its form, one through the genus predicated univocally of it, or one through a relation, or one through the term only. b If it is like Zaid and Amr individually differentiated and specifically one, then it necessarily possesses hyle, and this is impossible. If it is differentiated through its form, but one through the genus predicated univocally of it, then it is necessarily composite. If it is one in its genus, predicated by analogy to one thing, there is no objection, and one part of it will be the cause of another and the series will end in a first cause, and this is what happens with the forms abstracted from matter, according to the philosophers. If it is only common through the term, then there is no objection to its being more than one, and this is the case with the four primary causes, i. e. the first agent, the ultimate form, the ultimate end, the ultimate matter. ‘ Therefore, no strict proof is attained through this method, and one does not arrive at the First Principle as Avicenna thought; nor to its being necessarily one.

Ghazali says:

The second way is the drawing of the consequence, and we say: If existence, substantiality and being a principle are not a genus, because they do not give an answer to the question ‘What is it? ‘, then according to you the First is pure intellect just like the other intellects which are the principles of existence, called angels, according to the philosophers, and which are the effects of the First, are intellects separate from matter. And this abstract reality comprises the First and the first effect. This First, further, is according to the philosophers simple, and there is no compound in its essence except through its necessary attributes, and both the First Cause and the first effect participate in being intellect without matter. This, however, is a generic reality. Nor is intellectuality, separate from matter, a necessary attribute, for it is indeed a quiddity, and this quiddity is common to the First and all the other intellects. Therefore, if they do not differ in anything else, you have necessarily conceived a duality without a further difference; and if they do differ, what then is this distinction apart from their intellectuality, which they have in common? For what they have in common is participation in this abstract reality. For indeed the First is conscious of its own self and of others, according to those who believe that it is in its es3ence intellect separate from matter; and also the first effect, which is the first intellect which God has created without a mediator, participates in this characteristic. This proves that the intellects which are effects are different species, that they only participate in intellectuality and are besides this distinguished by specific differences, and that likewise the First participates with all the other intellects in this intellectuality. The philosophers, therefore, are either in plain contradiction to their own fundamental thesis, or have to affirm that intellectuality does not constitute God’s essence. And both positions are absurd according to them.

I say:

If you have understood what we have said before this, that there are things which have a term in common not univocally or equivocally, but by the universality of terms analogically related to one thing, and that the characteristic of these things is that they lead upwards to a first term in this genus which is the first cause of everything to which this word refers, like warmth, which is predicated of fire and all other warm things, and like the term ‘existent’ which is predicated of the substance and all other accidents, and like the term ‘movement’ predicated of motion in space and all the other movements, you will not have to occupy yourself with the mistakes in this reasoning. For the term ‘intellect’ is predicated analogically of the separate intellects according to the philosophers, and there is among them a first intellect which is the cause of all the other intellects, and the same thing is true of substance. And the proof that they have not one nature in common is that some of them are the causes of others and the cause of a thing is prior to the effect, and the nature of cause and effect cannot be one in genus except in the individual causes, and this kind of community is contradictory to genuine generic community, for things which participate in genus have no first principle which is the cause of all the others-they are all of the same rank, and there is no simple principle in them-whereas the things which participate in something predicated of them analogically must have a simple first principle. And in this First no duality can be imagined, for if a second were assumed, it must be of the same level of existence and of the same nature as the First, and they would have one nature in common in which they would participate by generic participation and would have to be distinguished through specific differences, additional to the genus, and both would be composed of genus and specific difference, and everything which is of this description is temporal; and lastly that which is of the extreme perfection i of existence must be unique, for if it were not unique, it could not be of the extreme perfection of existence, for that which is in the extreme degree cannot participate with anything else, for in the same way as one single line cannot have two extreme points at the same end, things extended in existence and differentiated through increase s and decrease have not two extremes at the same side. And since Avicenna was not aware of this nature, which stands midway between the nature of that which is univocally predicated and those natures which participate only through the equivocation of the term or in a distant, accidental way, this objection was valid against him.