[II.1] “The things we seek are equal etc.” (Quaestiones sunt aequales etc.) After it has been explained about demonstrative syllogism in the first book, Aristotle settles

the questions about the principles of demonstrative syllogism, and first about the middle of demonstration and the incomplex principle. And since every question is a question about the middle, the Philosopher first decides about questions. And he gives the number of questions, saying that the questions are equal in number to those things that we truly know, and therefore there are four questions.

[II.1 89b24-35] The first conclusion of this book is that there are four kinds of things known. This conclusion is proved thus: There are four things sought, and the <the kinds of> what is known are equal in number. If what is sought is of four kinds, therefore etc. That what is sought is of four kinds is obvious, for sometimes we seek if it is, sometimes what it is, sometimes whether it is so, and sometimes why it is so. Of these questions two are simple, not positing <more than one> in number, namely the questions if it is and what it is. And two are composite, positing <more than one> in number, and these are the question whether it is so, and why it is so.

Now it must be known that the question whether it is so (quia est) does not ask through the conjunction “quia,” for the conjunction “quia” is not a mark of a question. But the question “quia” asks through “utrum,” for instance, whether (utrum) a man is able to laugh. But the conjunction “quia non” is a mark establishing a question, (43vb) for if we ask whether (quia) a man is not (non) nothing

we ask whether (utrum) a man is nothing. And because of this the question is called the question “quia,” for this conjunction “quia non” is a mark establishing a question.

It must also be noted that the question if it is and the question what it is are simple questions, for these two questions ask about something incomplex, and the incomplex is simple. For if it is asked what man is, or if man is, the question is about man, and so about something incomplex. But the question whether it is so and why it is so are called composite questions because they ask about a complex, and the complex is composite. Or it can be said that sometimes something is asked about the subject that is outside the essence of the subject. If what is asked concerns the essence of the subject about which it is asked, then it is a simple question not positing <more than one> in number, since that which is about the essence of something does not, strictly speaking, posit <anything else> in the number with its subject. But if that which is asked is outside the nature of that about which it is asked,

then there is a composite question, positing <more than one> in number. For that which is outside the essence of another posits <something else> in the number with this <essence>. And since what is asked through the question what it is, and in the same way what is asked through the question if it is, is about the essence of that about which it is asked, therefore the question what it is and if it is are simple questions not positing <more than one> in number. And since what is asked through the question why it is so, and in the same way through the question whether it is so, is outside the essence of that about which it is asked, therefore the question why it is so

and the question whether it is so are composite questions positing <more than one> in number.

[II.2] The second conclusion of this book is that the question whether it is and the question if it is ask about the middle <term>, if it is. This conclusion is proved thus: For it is nothing other to ask about something whether (an) it is than to ask if there is a middle term from which it is suitable to conclude that it is.

Therefore one asks the question if it is concerning the middle, if it is. Again, it is nothing other to ask whether the moon is eclipsed than to ask if there is a middle term from which it is suitable to conclude that the moon is eclipsed. And so the question if it is and the question whether it is so ask about the middle term, if it is.

[II.2 90a8-15] The third conclusion is this, that the question what it is and the question why it is so ask about the middle term, what it is. This conclusion is proved thus: The question what it is and the question why it is so ask the same thing. But the question what it is asks what the middle is. Therefore the question why it is so asks what the middle is. That these questions ask the same thing is obvious. For questions ask the same thing when, in answering them (illae quaestiones idem quaerunt ad quas), the same <conclusion> is demonstrated through the same <principles>. But these are of this sort, therefore etc.

[II.2 90a5-6] The fourth conclusion is this, that in every conclusion it is either asked what the middle is or if the middle is. This conclusion is proved thus: As it follows from what was said, for the question whether it is so and the question if it is ask if there is a middle, but the question what it is and why it is so ask what the middle is. But every question is either a question if <the middle> is, or a question what it is, therefore etc.

[II.3 esp. 90b2-7] The fifth conclusion of this book is that there is not a definition of every reality concerning which there is a demonstration. This conclusion is proved thus: Definition indicates what it is (quod quid est). But what it is is predicated universally and affirmatively of that of which it is. But not every demonstration is demonstrative of an universal affirmative conclusion. There are some negative demonstrations, for instance, demonstrations in the second figure. And there are some particular demonstrations, for instance, those that arise in the third figure. Therefore there is not a definition of everything of which there is a demonstration.

[II.3 90b19-27] The sixth conclusion concerns whether there is a demonstration concerning everything of which there is a definition. This conclusion is proved thus, through an argument that was made above, which is this: Of one <genus> considered as it is one there is one science, and one per se producer of knowing. If, then, there is demonstration concerning whatever reality has a definition, since we know that of which there is a definition in having a definition of it, and of one reality there is one knowledge. It would follow, then, that without demonstration we know what is knowable through demonstration, which is impossible. For a knowable through demonstration is not known except through demonstration.

[II.3 90b25-27] The seventh conclusion is this, that not every reality is known through demonstration that is known through definition. This is proved more especially because <if every reality were> it would follow that the principles of demonstration are demonstration, and thus there is a process into infinity; but this is impossible.

[II.3 90b28-33] The eighth conclusion concerns whether the definition and demonstration of any reality is the same. And it is proved that it is not, thus: Definition is the manifestation of the what-it-is of the subject. But demonstrations do not make the what-it-is manifest, but presuppose this. For instance, arithmetic presupposes the what-it-is of unity, and what the odd is, hence there is no demonstration of this.

[II.4] The ninth (44ra) conclusion is that demonstrations or syllogisms do not produce knowing the definition of the defined, in the way in which there is a definition explaining what the reality is and what the being of the reality is. This conclusion is proved thus: If it is to be proved that B is A in what is is <i.e., in its essence>, it is necessary that this modifying phrase “in what it is” be present in both premisses. If this modifying phrase is in neither premises, or is not in one of them, then the conclusion that B is A in what it is does not follow. For it does not follow that since every C is A, and B is C, therefore B is A in what it is. Nor does it follow that since B is A in what it is, and C is B, therefore C is A in what it is. But this follows well enough, every C is A in what it is, and every B is C in what it is, therefore every B is A in what it is. For the conclusion to follow in what it is, it is necessary that the modifying phrase “in what it is” be joined with A in the major premise and with C in the minor premise. But such a syllogism does not make us know its conclusion, since before the conclusion of such a syllogism it is necessary to assume the defining phrase, and so in such a syllogism there is a begging of the question, since that which is to be concluded is presupposed in the premisses. And so it is clear that neither through syllogism nor demonstration can the defining phrase be concluded through a middle term.

[II.5] The tenth conclusion is this, that the definition is not, considered as a definition, concluded of the defined by the way of division. This conclusion is proved thus: It is necessary for what is concluded through definition to be true if the premisses are true, but in every demonstration it is necessary for the conclusion to be true if the premisses are true; therefore the definition, considered as it unfolds what is defined, is not concluded of the defined through division, nor is it demonstrated, nor is it syllogized. For if the divider demonstrated and syllogized, it would not be necessary to ask in the end concerning the conclusion, rather it would be necessary that every conclusion be due to its premisses whether the respondent granted it or not.

[II.6] The eleventh conclusion is that a defining expression is not demonstrated of what is defined through a middle term by a definitional showing, <but> it concludes such expressions through the way in which it is a method of definition. The definition of man is “rational mortal animal,” but this expression is not a definition unfolding what man is <i.e. not a formal definition>. Hence if this definition, “rational mortal animal,” the definition of man, is to be proved through a defining expression,

then it is proved thus: Every form convertible with man constituted from the genus and difference of man is the definition of man, rational mortal animal is of this sort, therefore etc. But the definition is not demonstrated in this way of what it is of, which is clear since in this argument there is a begging of the question, for it asks us to assume what is to be proved. For a definition is to be proved of the defined and it <a definition> is asked for in this argument, for it must be accepted that “every convertible form constituted from the genus and difference” is the definition of definition, and since a definition is to be proved, therefore etc.

[II.7-8 93a15-28] The twelfth conclusion

is that the definition is demonstrated though the middle because the middle is a definition, but the demonstration does not show the definition as a definition unfolding what a reality is [i.e. a formal definition], as was proved above. And this conclusion is proved thus: For it is the same thing to know the what-it-is and the cause of the reality, since the cause and the definition are the same. But a definition has a cause why it is in the defined, and the middle of demonstration is a cause convertible with the subject. Therefore the definition will be demonstrated of the subject through the definition of the subject.

Hence the subject can have several definitions just as it may have several causes. For different demonstrations arise from different causes. And causes are causes to one another. For as the form is the cause, so the definition received from the formal cause is the cause of the definition received from the material cause. And therefore the definition received from the material cause can be concluded from the definition received from the formal cause. The Philosopher says in the text that the cause is the same as the reality, or other [93a4 ff.]. And Grosseteste says that this is to be understood thus, that the cause that is the same as the reality is the formal cause, for the form is the entire and true being of the reality which has it in it. And if the form does not need matter it is the true reality itself, and a form that needs matter, if it can sustain itself without matter, is more truly the reality itself than the reality with matter. Thus, if the form of a statue could be without matter it would be more truly this figure than the statue enmattered. The cause, then, <is> formal, and the definition is taken from the formal cause, and by this argument it must be the same as the reality. Therefore the final and efficient causes are outside the reality. But the material cause, though it is of the reality necessarily, still it is not due to the power of the essence, and it is taken on necessarily because if Socrates is then it is necessary for him to be some matter. And for this reason three of the causes and the definitions taken from two of them are all said to be other than the reality here.

Others say that matter (44rb) and form, which are intrinsic parts of the reality, are said to be the same as the reality, but the efficient and final causes, which are by extrinsic being, are other than the reality, therefore etc.

[93a29-b7] The thirteenth conclusion is that through what it is we know if it is without qualification. And this conclusion is proved thus: Knowing is through the cause, and the cause and the definition are the same, therefore knowing is through the definition. Therefore if it is is known through the definition, also, then, through what it is, we know if it is without qualification.

[93b15-20] And the Philosopher explains this through an example in the fourteenth conclusion, which is this: A definition can be drawn from every demonstration, and a demonstration from every definition. But if a definition is had from a demonstration, if that definition <considered as formal> be made a syllogistic middle it can be demonstrated <considered as material> of the defined through a demonstration that it is so <and not of the reason why>, and in the same way, if it is a formal definition it can demonstrate a material definition of the defined.

[II.9 93b21-28] The fifteenth conclusion is that a formal definition is a demonstrator of the material definition of the defined, and the formal definition is not demonstrated of the defined.

For material definition is demonstrated of the defined through formal definition, and from this it follows that a definition composed of material and formal definition is a demonstration with its parts moved to different places. And this conclusion is proved thus: Formal definition is the cause of the material definition, and not conversely; but the cause demonstrates the caused, therefore the formal definition demonstrates the material definition.