Chapter VIII: Analytica Posteriora II (1)

Aristotle begins the Second Book of the Analytica Posteriora by an enumeration and classification of Problems or Questions suitable for investigation. The matters knowable by us may be distributed into four classes:--

[Greek: O(/ti]. [Greek: Dio/ti]. [Greek: Ei) e)/sti]. [Greek: Ti/ e)sti].

1. Quod. 2. Cur. 3. An sit. 4. Quid sit.

Under the first head come questions of Fact; under the second head, questions of Cause or Reason; under the third, questions of Existence; under the fourth, questions of Essence. Under the first head we enquire, Whether a fact or event is so or so? Whether a given subject possesses this or that attribute, or is in this or that condition? enumerating in the question the various supposable alternatives. Under the second head, we assume the first question to have been affirmatively answered, and we proceed to enquire, What is the cause or reason for such fact, or such conjunction of subject and attribute? Under the third head, we ask, Does a supposed subject exist? And if the answer be in the affirmative, we proceed to enquire, under the fourth head, What is the essence of the subject?[1]

[Footnote 1: Analyt. Post. II. i. p. 89, b. 23, seq. Themistius observes, p. 67, Speng.: [Greek: zêtou=men ti/nun ê)\ peri\ a(plou= tino\s kai\ a)sunthe/tou, ê)\ peri\ sunthe/tou kai\ e)n prota/sei.] Themistius has here changed Aristotle's order, and placed the third and fourth heads before the first and second. Compare Schol. p. 240, b. 30; p. 241, a. 18. The Scholiast complains of the enigmatical style of Aristotle: [Greek: tê=| griphô/dei tou= r(êtou= e)paggeli/a] (p. 240, b. 25).]

We have here two distinct pairs of _Quæsita_: Obviously the second head presupposes the first, and is consequent thereupon; while the fourth also presupposes the third. But it might seem a more suitable arrangement (as Themistius and other expositors have conceived) that the third and fourth heads should come first in the list, rather than the first and second; since the third and fourth are simpler, and come earlier in the order of philosophical exposition, while the first and second are more complicated, and cannot be expounded philosophically until after the philosophical exposition of the others. This is cleared up by adverting to the distinction, so often insisted on by Aristotle, between what is first in order of cognition relatively to us (_nobis notiora_), and what is first in order of cognition by nature (_naturâ notiora_). _To us_ (that is to men taken individually and in the course of actual growth) the phenomena of nature[2] present themselves as particulars confused and complicated in every way, with attributes essential and accidental implicated together: we gradually learn first to see and compare them as particulars, next to resolve them into generalities, bundles, classes, and partially to explain the _Why_ of some by means of others. Here we start from facts embodied in propositions, that include subjects clothed with their attributes. But in the _order of nature_ (that is, in the order followed by those who know the _scibile_ as a whole, and can expound it scientifically) that which comes first is the Universal or the simple Subject abstracted from its predicates or accompaniments: we have to enquire, first, whether a given subject exists; next, if it does exist, what is its real constituent essence or definition. We thus see the reason for the order in which Aristotle has arranged the two co-ordinate pairs of _Quæsita_ or Problems, conformable to the different processes pursued, on the one hand, by the common intellect, growing and untrained--on the other, by the mature or disciplined intellect, already competent for philosophical exposition and applying itself to new _incognita_.

[Footnote 2: **Schol. Philopon. p. 241, a. 18-24: [Greek: tou/tôn to\ ei) e)/sti kai\ to\ ti/ e)stin ei)si\n a(pla=, to\ de\ o(/ti kai\ to\ dio/ti su/ntheta--pro/tera ga\r ê(mi=n kai\ gnôrimô/tera ta\ su/ntheta, ô(s tê=| phu/sei ta\ a(pla=.]

Mr. Poste observes upon this quadruple classification by Aristotle (p. 96):--"The two last of these are problems of Inductive, but first principles of Deductive, Science; the one being the hypothesis, the other the definition. The **attribute as well as the subject must be defined (I. x.), so that to a certain degree the second problem also is assumed among the principles of Demonstration."]

Comparing together these four _Quæsita_, it will appear that in the first and third (_Quod_ and _An_), we seek to find out whether there is or is not any middle term. In the second and fourth (_Cur_ and _Quid_), we already know or assume that there is a middle term; and we try to ascertain what that middle term is.[3] The enquiry _Cur_, is in the main analogous to the enquiry _Quid_; in both cases, we aim at ascertaining what the cause or middle term is. But, in the enquiry _Cur_, what we discover is perhaps some independent fact or event, which is the cause of the event _quæsitum_; while, in the enquiry _Quid_, what we seek is the real essence or definition of the substance--the fundamental, generating, immanent cause of its concomitant attributes. Sometimes, however, the _Quid_ and the _Cur_ are only different ways of stating the same thing. _E.g._, _Quid est eclipsis lunæ_? Answer: The essence of an eclipse is a privation of light from the moon, through intervention of the earth between her and the sun. _Cur locum habet eclipsis lunæ_? Answer: Because the light of the sun is prevented from reaching the moon by intervention of the earth. Here it is manifest that the answers to the enquiries _Quid_ and _Cur_ are really and in substance the same fact, only stated in different phrases.[4]

[Footnote 3: Analyt. Post. II. i. p. 889, b. 37-p. 90, a. 7. [Greek: sumbai/nei a)/ra e)n a(pa/sais tai=s zêtê/sesi zêtei=n ê)\ ei) e)/sti me/son, ê)\ ti/ e)sti to\ me/son; to\ me\n ga\r ai)/tion to\ me/son, e)n a(/pasi de\ tou=to zêtei=tai.] Compare Schol. p. 241, b. 10, Br.]

[Footnote 4: Analyt. Post. II. ii. p. 90, a. 14-23, 31: [Greek: to\ ti/ e)stin ei)de/nai tau)to/ e)sti kai\ dia\ ti/ e)stin.]]

That the _quæsitum_ in all these researches is a middle term or medium, is plain from those cases wherein the medium is perceivable by sense; for then we neither require nor enter upon research. For example, if we were upon the moon, we should see the earth coming between us and the sun, now and in each particular case of eclipse. Accordingly, after many such observations, we should affirm the universal proposition, that such intervention of the earth was the cause of eclipses; the universal becoming known to us through induction of particular cases.[5] The middle term, the Cause, the _Quid_, and the _Cur_, are thus all the same enquiry, in substance; though sometimes such _quæsitum_ is the quiddity or essential nature of the thing itself (as the essence of a triangle is the cause or ground of its having its three angles equal to two right angles, as well as of its other properties), sometimes it is an extraneous fact.[6]

[Footnote 5: Ibid. a. 24-30. [Greek: e)k ga\r tou= ai)sthe/sthai kai\ to\ katho/lou e)ge/neto a)\n ê(mi=n ei)de/nai; ê( me\n ga\r ai)/sthêsis o(/ti nu=n a)ntiphra/ttei; kai\ ga\r dê=lon o(/ti nu=n e)klei/pei; e)k de\ tou/tou to\ katho/lou a)\n e)ge/neto.]

The purport and relation of this quadruple classification of problems is set forth still more clearly in the sixth book of the Metaphysica (Z. p. 1041) with the explanations of Bonitz, Comm. pp. 358, 359.]

[Footnote 6: Analyt. Post. II. ii. p. 90, a. 31.]

But how or by what process is this _quæsitum_ obtained and made clear? Is it by Demonstration or by Definition? What is Definition, and what matters admit of Definition?[7] Aristotle begins by treating the question dialectically; by setting out a series of doubts and difficulties. First, Is it possible that the same cognition, and in the same relation, can be obtained both by Definition and by Demonstration? No; it is not possible. It is plain that much that is known by Demonstration cannot be known by Definition; for we have seen that conclusions both particular and negative are established by Demonstration (in the Third and Second figures), while every Definition is universal and affirmative. But we may go farther and say, that even where a conclusion universal and affirmative is established (in the First figure) by Demonstration, that same conclusion can never be known by Definition; for if it could be known by Definition, it might have been known without Demonstration. Now we are assured, by an uncontradicted induction, that this is not the fact; for that which we know by Demonstration is either a proprium of the subject _per se_, or an accident or concomitant; but no Definition ever declares either the one or the other: it declares only the essence.[8]

[Footnote 7: Ibid. iii. p. 90, a. 37: [Greek: ti/ e)stin o(rismo/s, kai\ ti/nôn, ei)/pômen, diaporê/santes prô=ton peri\ au)tô=n.]]

[Footnote 8: Analyt. Post. II. iii. p. 90, b. 13: [Greek: i(kanê\ de\ pi/stis kai\ e)k tê=s e)pagôgê=s; ou)de\n ga\r pô/pote o(risa/menoi e)/gnômen, ou)/te tô=n kath' au(to\ u(parcho/ntôn ou)/te tô=n sumbebêko/tôn. e)/ti ei) o( o(rismo\s ou)si/as tis gnôrismo/s, ta\ ge toiau=ta phanero\n o(/ti ou)k ou)si/ai.]]

Again, let us ask, _vice versâ_, Can everything that is declared by Definition, or indeed anything that is declared by Definition, be known also by Demonstration? Neither is this possible. One and the same _cognitum_ can be known only by one process of cognition. Definitions are the _principia_ from which Demonstration departs; and we have already shown that in going back upon demonstrations, we must stop somewhere, and must recognize some _principia_ undemonstrable.[9] The Definition can never be demonstrated, for it declares only the essence of the subject, and does not predicate anything concerning the subject; whereas Demonstration assumes the essence to be known, and deduces from such assumption an attribute distinct from the essence.[10]

[Footnote 9: Ibid. b. 18-27.]

[Footnote 10: Ibid. b. 33, seq.: [Greek: e)/ti pa=sa a)po/deixis ti\ kata/ tinos dei/knusin, oi(=on o(/ti e)/stin ê)\ ou)k e)/stin; e)n de\ tô=| o(rismô=| ou)de\n e(/teron e(te/rou katêgorei=tai, oi(=on ou)/te to\ zô=|on kata\ tou= di/podos ou)de\ tou=to kata\ tou= zô=|ou--o( me\n ou)=n o(rismo\s ti/ e)sti dêloi=, ê( de\ a)po/deixis o(/ti ê)\ e)/sti to/de kata\ tou=de ê)\ ou)k e)/stin.]

Themistius (p. 71, Speng.) distinguishes the [Greek: o(rismo/s] itself from [Greek: ê( pro/tasis ê( to\n o(rismo\n katêgorou/menon e)/chousa].]

Prosecuting still farther the dialectical and dubitative treatment,[11] Aristotle now proceeds to suggest, that the Essence (that is, the entire Essence or Quiddity), which is declared by Definition, can never be known by Demonstration. To suppose that it could be so known, would be inconsistent with the conditions of the syllogistic proof used in demonstrating. You prove by syllogism, through a middle term, some predicate or attribute; _e.g._ because A is predicable of all B, and B is predicable of all C, therefore A is predicable of all C. But you cannot prove, through the middle term B, that A is the essence or quiddity of C, unless by assuming in the premisses that B is the essence of C, and that A is the essence of B; accordingly, that the three propositions, AB, BC, AC, are all co-extensive and reciprocate with each other. Here, then, you have assumed as your premisses two essential propositions, AB, BC, in order to prove as an essential proposition the conclusion AC. But this is inadmissible; for your premisses require demonstration as much as your conclusion. You have committed a _Petitio Principii_;[12] you have assumed in your minor premiss the very point to be demonstrated.

[Footnote 11: Analyt. Post. II. iv. p. 91, a. 12: [Greek: tau=ta me\n ou)=n me/chri tou/tou diêporê/sthô]. One would think, by these words, that [Greek: to\ diaporei=n] (or the dubitative treatment) finished here. But the fact is not so: that treatment is continued for four chapters more, to the commencement of ch. viii. p. 93.]

[Footnote 12: Analyt. Post. II. iv. p. 91, a. 12-32: [Greek: tau=ta d' a)na/gkê antistre/phein; ei) ga\r to\ A tou= G i)/dion, dê=lon o(/ti kai\ tou= B kai\ tou=to tou= G, ô(/ste pa/nta a)llê/lôn.--lamba/nei ou)=n o(\ dei= dei=xai; kai\ ga\r to\ B e)/sti ti/ e)stin a)/nthrôpos.] Themistius, pp. 72, 73: [Greek: to\n a)podeiknu/nta to\ ti/ ê)=n ei)=nai tou= a)nthrô/pou, a)/llo ti dei= prolabei=n tou= au)tou= to\ ti/ ê)=n ei)=nai.--ou(= ga\r bou/letai to\n o(rismo\n a)podei=xai, tou/tou prolamba/nei tina\ o(rismo\n ei)=nai chôti\s a)podei/xeôs.]

M. Barthélemy St. Hilaire, notes, p. 205:--"Il faut donc, pour conclure par syllogisme que A est la définition essentielle de C, que A soit la définition essentielle de B, et que B soit lui-même la définition essentielle de C. Mais alors la définition de la chose sera dans le moyen terme lui-même, avant d'être dans la conclusion; en effet, la mineure: B est la définition essentielle de C, donne la définition essentielle de C, sans qu'il soit besoin d'aller jusqu'**à la conclusion. Donc la démonstration de l'essence ainsi entendue est absurde."]

If you cannot obtain Definition as the conclusion of syllogistic Demonstration, still less can you obtain it through the method of generic and specific Division; which last method (as has been already shown in the Analytica Priora) is not equal even to the Syllogism in respect of usefulness and efficacy.[13] You cannot in this method distinguish between propositions both true and essential, and propositions true but not essential; you never obtain, by asking questions according to the method of generic subdivision, any premisses from which the conclusion follows by necessity. Yet this is what you ought to obtain for the purpose of Demonstration; for you are not allowed to enunciate the full actual conclusion among the premisses, and require assent to it. Division of a genus into its species will often give useful information, as Induction also will;[14] but neither the one nor the other will be equivalent to a demonstration. A definition obtained only from subdivisions of a genus, may always be challenged, like a syllogism without its middle term.

[Footnote 13: Analyt. Post. II. v. p. 91, b. 12, seq.; Analyt. Prior. I. xxxi. p. 46, a. 31. Aristotle here alludes to the method pursued by Plato in the Sophistes and Politicus, though he does not name Plato: [Greek: ê( dia\ tô=n diaire/seôn o(do/s], &c.]

[Footnote 14: Analyt. Post. II. v. p. 91, b. 15-33: [Greek: ou)de\ ga\r o( e)pa/gôn i)/sôs a)podei/knusin, a)ll' o(/môs dêloi= ti.] Compare Themistius, p. 74.]

Again, neither can you arrive at the definition of a given subject, by assuming in general terms what a definition ought to be, and then declaring a given form of words to be conformable to such assumption; because your minor premiss must involve _Petitio Principii_. The same logical fault will be committed, if you take your departure from an hypothesis in which you postulate the definition of a certain subject, and then declare inferentially what the definition of its contrary must be. The definition which you here assume requires proof as much as that which you infer from it.[15] Moreover, neither by this process, nor by that of generic subdivision, can you show any reason why the parts of the definition should coalesce into one essential whole. If they do not thus coalesce--if they be nothing better than distinct attributes conjoined in the same subject, like _musicus_ and _grammaticus_--the real essence is not declared, and the definition is not a good one.[16]

[Footnote 15: Analyt. Post. II. vi. p. 92, a. 6-28. Themist. p. 76.

Rassow renders [Greek: e)x u(pothe/seôs]--"assumptâ generali definitionis notione;" and also says: "[Greek: to\ ti/ ê)=n ei)=nai]--generalem definitionis notionem; [Greek: to\ ti/ e)stin]--certam quandam definitionem, significare perspicuum est." (Aristotelis de Notionis Definitione Doctrina, p. 65).]

[Footnote 16: Analyt. Post. II. vi. p. 92, a. 32. That the parts of the definition must coalesce into one unity is laid down again in the Metaphysica, Z. pp. 1037, 1038, where Aristotle makes reference to the Analytica as haying already treated the same subject, and professes an intention to complete what has been begun in the Analytica; [Greek: e)ph' o(/son e)n toi=s A)nalutikoi=s peri\ o(rismou= mê\ ei)/rêtai.]]

After stating some other additional difficulties which seem to leave the work of Definition inexplicable, Aristotle relinquishes the dubitative treatment, and looks out for some solution of the puzzle: How may it be possible that the Definition shall become known?[17] He has already told us that to know the essence of a thing is the same as to know the cause or reason of its existence; but we must first begin by knowing that the _definiendum_ exists; for there can be no definition of a non-entity, except a mere definition of the word, a nominal or verbal definition. Now sometimes we know the existence of the subject by one or other of its accidental attributes; but this gives us no help towards finding the definition.[18] Sometimes, however, we obtain a partial knowledge of its essence along with the knowledge of its existence; when we know it along with some constant antecedent, or through some constant, though derivative, consequent. Knowing thus much, we can often discover the cause or fundamental condition thereof, which is the essence or definition of the subject.[19] Indeed, it may happen that the constant derivative, and the fundamental essence on which it depends, become known both together; or, again, the cause or fundamental condition may perhaps not be the essence of the subject alone, but some fact including other subjects also; and this fact may then be stated as a middle term. Thus, in regard to eclipse of the moon, we know the constant phenomenal fact about it, that, on a certain recurrence of the time of full moon, the moon casts no light and makes no shadow. Hence we proceed to search out the cause. Is it interposition of the earth, or conversion of the moon's body, or extinction of her light, &c.? The new fact when shown, must appear as a middle term, throwing into syllogistic form (in the First figure) the cause or rational explanation of a lunar eclipse; showing not merely that there is an eclipse, but what an eclipse is, or what is its definition.[20]

[Footnote 17: Analyt. Post. II. vii. p. 92, a. 34, seq. The [Greek: a)po/riai] continue to the end of ch. vii. He goes on, ch. viii. p. 93, a. 1-2: [Greek: pa/lin de\ skepte/on ti/ tou/tôn le/getai kalô=s, kai\ ti/ ou) kalô=s], &c. "Tout ce qui précède ne représente pas la théorie proprement dite; ce n'est qu'une discussion préliminaire" (Barth. St. Hilaire, not. p. 222). These difficult chapters are well illustrated by Hermann Rassow, ch, i. pp. 9-14.]

[Footnote 18: Analyt. Post. II. viii. p. 93, a. 3: [Greek: e)pei\ d' e)sti/n, ô(s e)/phamen, tau)to\n to\ ei)de/nai ti/ e)sti kai\ to\ ei)de/nai to\ ai)/tion tou= ei) e)/sti;] Ibid. a. 24: [Greek: o(/sa me\n ou)=n kata\ sumbebêko\s oi)/damen o(/ti e)/stin, a)nagkai=on mêdamô=s e)/chein pro\s to\ ti/ e)stin; **ou)de\ ga\r o(/ti e)/stin i)/smen; to\ de\ zêtei=n ti/ e)sti mê\ e)/chontas o(/ti e)/sti, mêde\n zêtei=n e)sti/n. kath' o(/sôn d' e)/chome/n ti, r(a=|on; ô(/ste ô(s e)/chomen o(/ti e)/stin, ou(/tôs e)/chomen kai\ pro\s to\ ti/ e)stin.] Compare Brentano, Ueber die Bedeutung des Seienden nach Aristoteles, p. 17.]

[Footnote 19: Analyt. Post. II. viii. p. 93, a. 21. Themistius, p. 79, Speng.: [Greek: o(/sa de\ a)po\ tô=n oi)kei/ôn te kai\ e)x au)tou= tou= pra/gmatos, a)po\ tou/tôn ê)/dê r(a=|on ei)s to\ ti/ e)sti metabai/nomen.]]

[Footnote 20: Ibid. p. 93, a. 30-b. 14.]

Aristotle has thus shown how the Essence or Quiddity ([Greek: ti/ e)sti]) may become known in this class of cases. There is neither syllogism nor demonstration thereof, yet it is declared through syllogism and demonstration: though no demonstration thereof is possible, yet you cannot know it without demonstration, wherever there is an extraneous cause.[21]

[Footnote 21: Ibid. b. 15-20: [Greek: ô(/ste sullogismo\s me\n tou= ti/ e)stin ou) gi/netai ou)d' a)po/deixis, dê=lon me/ntoi dia\ sullogismou= kai\ di' a)podei/xeôs.]

Mr. Poste translates an earlier passage (p. 93, a. 5) in this very difficult chapter as follows (p. 107): "If one cause is demonstrable, another indemonstrable cause must be the intermediate; and the proof is in the first figure, and the conclusion affirmative and universal. In this mode of demonstrating the essence, we prove one definition by another, for the intermediate that proves an essence or a peculiar predicate must itself be an essence or a peculiar predicate. Of two definitions, then, one is proved and the other assumed; and, as we said before, this is not a demonstration but a dialectical proof of the essence." Mr. Poste here translates [Greek: logiko\s sullogismo/s] "dialectical proof." I understand it rather as meaning a syllogism, [Greek: tou= u(pa/rchein] simply (Top. I. v. p. 102, b. 5), in which all that you really know is that the predicate belongs to the subject, but in which you _assume_ besides that it belongs to the subject _essentially_. It is not a demonstration because, in order to obtain Essence in the conclusion, you are obliged to postulate Essence in your premiss. (See Alexander ad Topic. I. p. 263, Br.). You have therefore postulated a premiss which required proof as much as the conclusion.]

But the above doctrine will hold only in cases where there _is_ a distinct or extraneous cause; it will not hold in cases where there is none. It is only in the former (as has been said) that a middle term can be shown; rendering it possible that Quiddity or Essence should be declared by a valid formal syllogism, though it cannot be demonstrated by syllogism. In the latter, where there is no distinct cause, no such middle term can be enunciated: the Quiddity or Essence must be assumed as an immediate or undemonstrable principium, and must be exposed or set out in the best manner practicable as an existent reality, on Induction or on some other authority. The arithmetician makes his first steps by assuming both what a monad is and that there exists such a monad.[22]

[Footnote 22: Analyt. Post. II. ix. p. 93, b. 21. [Greek: e)/sti de\ tô=n me\n e(/tero/n ti ai)/tion, tô=n d' ou)k e)/stin. ô(/ste dê=lon o(/ti kai\ tô=n ti/ e)sti ta\ me\n a)/mesa kai\ a)rchai/ ei)sin, a(\ kai\ ei)=nai kai\ ti/ e)stin u(pothe/sthai dei= ê)\ a)/llon tro/pon phanera\ poiê=sai. o(/per o( a)rithmêtiko\s poiei=; kai\ ga\r ti/ e)sti tê\n mona/da u(poti/thetai, kai\ o(/ti e)/stin.]

Themistius, p. 80: [Greek: a(\ kai\ ei)=nai kai\ ti/ e)stin u(pothe/sthai dei=, ê)\ a)/llon tro/pon phanera\ poiê=sai e)x e)pagôgê=s ê)\ pi/steôs ê)\ e)mpeiri/as.] Rassow, De Notionis Definitione, pp. 18-22.]

We may distinguish three varieties of Definition. 1. Sometimes it is the mere explanation what a word signifies; in this sense, it has nothing to do with essence or existence; it is a nominal definition and nothing more.[23] 2. Sometimes it enunciates the Essence, cause, or reason of the _definitum_; this will happen where the cause is distinct or extraneous, and where there is accordingly an intervening middle term: the definition will then differ from a demonstration only by condensing into one enunciation the two premisses and the conclusion which together constitute the demonstration.[24] 3. Sometimes it is an immediate proposition, an indemonstrable hypothesis, assuming Essence or Quiddity; the essence itself being cause, and no extraneous cause--no intervening middle term--being obtainable.[25]

[Footnote 23: Analyt. Post. II. x. p. 93, b. 29-37.]

[Footnote 24: Ibid. p. 93, b. 38, seq. [Greek: oi(=on a)po/deixis tou= ti/ e)stin, tê=| the/sei diaphe/rôn tê=s a)podei/xeôs;--sullogismo\s tou= ti/ e)sti, ptô/sei diaphe/rôn tê=s a)podei/xeôs]--differing "situ et positione terminorum" (Julius Pacius, p. 493).]

[Footnote 25: Ibid. p. 94, a. 9: [Greek: o( de\ tô=n a)me/sôn o(rismo/s, the/sis e)sti\ tou= ti/ e)stin a)napo/deiktos.] Compare I. xxiv. p. 85, b. 24: [Greek: ô(=| ga\r kath' au(to\ u(pa/rchei ti, tou=to au)to\ au(tô=| ai)/tion.] See Kampe, Die Erkenntniss-theorie des Aristoteles, p. 212, seq.]

To know or cognize is, to know the Cause; when we know the Cause, we are satisfied with our cognition. Now there are four Causes, or varieties of Cause:--

1. The Essence or Quiddity (Form)--[Greek: to\ ti/ ê)=n ei)=nai].

2. The necessitating conditions (Matter)--[Greek: to/ ti/nôn o)/ntôn a)na/gkê tou=t' ei)=nai].

3. The proximate mover or stimulator of change (Efficient)--[Greek: ê( ti/ prô=ton e)ki/nêse].

4. That for the sake of which (Final Cause or End)--[Greek: to\ ti/nos e(/neka].

All these four Causes (Formal, Material, Efficient, Final) appear as middle terms in demonstrating. We can proceed through the medium either of Form, or of Matter, or of Efficient, or of End. The first of the four has already been exemplified--the demonstration by Form. The second appears in demonstrating that the angle in a semi-circle is always a right angle; where the middle term (or matter of the syllogism, ([Greek: to\ e)x ou(=]) is, that such angle is always the half of two right angles.[26] The Efficient is the middle term, when to the question, Why did the Persians invade Athens? it is answered that the Athenians had previously invaded Persia along with the Eretrians. (All are disposed to attack those who have attacked them first; the Athenians attacked the Persians first; _ergo_, the Persians were disposed to attack the Athenians.) Lastly, the Final Cause serves as middle term, when to the question, Why does a man walk after dinner? the response is, For the purpose of keeping up his health. In another way, the middle term here is digestion: walking after dinner promotes digestion; digestion is the efficient cause of health.[27]

[Footnote 26: Analyt. Post. II. xi. p. 94, a. 21-36. Themistius, p. 83: [Greek: ma/lista me\n ga\r e)pi\ pa/sês a)podei/xeôs o( me/sos e)/stin oi(=on ê( u(/lê tô=| sullogismô=|; ou(/tos ga\r o( poiô=n ta\s du/o prota/seis, e)ph' ai(=s to\ sumpe/rasma.]]

[Footnote 27: Analyt. Post. II. xi. p. 94, a. 36-b. 21.]

The Final Cause or End is prior in the order of nature, but posterior to the terms of the conclusion in the order of time or generation; while the Efficient is prior in the order of time or generation. The Formal and Material are simultaneous with the effect, neither prior nor posterior.[28] Sometimes the same fact may proceed both from a Final cause, and from a cause of Material Necessity; thus the light passes through our lantern for the purpose of guiding us in the dark, but also by reason that the particles of light are smaller than the pores in the glass. Nature produces effects of finality, or with a view to some given end; and also effects by necessity, the necessity being either inherent in the substance itself, or imposed by extraneous force. Thus a stone _falls_ to the ground by necessity of the first kind, but _ascends_ by necessity of the second kind. Among products of human intelligence some spring wholly from design without necessity; but others arise by accident or chance and have no final cause.[29]

[Footnote 28: Analyt. Post. II. xi. p. 94, a. 21-26. Themistius, p. 83: [Greek: ê( ge/nesis ou)=n tou= me/sou kai\ ai)ti/ou tê\n au)tê\n ou)k e)/chei ta/xin e)ph' a(pa/ntôn, a)ll' ou(= me\n prô/tên ô(s e)pi\ tô=n kinêtikô=n, ou(= de\ teleutai/an ô(s e)pi\ tô=n telô=n kai\ ô(=n e(/neka, ou(= d' a(/ma ô(s e)pi\ tô=n o(rismô=n kai\ tou= ti/ ê)=n ei)=nai.]]

[Footnote 29: Analyt. Post. II. p. 94, b. 27-p. 95, a. 9.]

That the middle term is the Cause, is equally true in respect to _Entia_, _Fientia_, _Præterita_, and _Futura_; only that in respect to _Entia_, the middle term or Cause must be an _Ens_; in respect to _Fientia_ it must be a _Fiens_; in respect to _Præterita_, a _Præteritum_; and in respect to _Futura_, a _Futurum_; that is, in each case, it must be generated at the corresponding time with the major and minor terms in the conclusion.[30] What is the cause of an eclipse of the moon? The cause is, that the earth intervenes between moon and sun; and this is true alike of eclipses past, present, and future. Such an intervention is the essence or definition of a lunar eclipse: the cause is therefore Formal, and cause and effect are simultaneous, occurring at the same moment of time. But in the other three Causes--Material, Efficient, Final--where phenomena are successive and not simultaneous, can we say that the antecedent is cause and the consequent effect, time being, as seems to us, a _continuum_? In cases like this, we can syllogize from the consequent backward to the antecedent; but not from the antecedent forward to the consequent. If the house has been built, we can infer that the foundations have been laid; but, if the foundations have been laid, we cannot infer that the house has been built.[31] There must always be an interval of time during which inference from the antecedent will be untrue; perhaps, indeed, it may never become true. Cause and _causatum_ in these three last varieties of Cause, do not universally and necessarily reciprocate with each other, as in the case of the Formal cause. Though time is continuous, events or generations are distinct points marked in a continuous line, and are not continuous with each other.[32] The number of these points that may be taken is indeed infinite; yet we must assume some of them as ultimate and immediate _principia_, in order to construct our syllogism, and provide our middle term.[33] Where the middle term reciprocates and is co-extensive with the major and the minor, in such cases we have generation of phenomena in a cycle; _e.g._, after the earth has been made wet, vapour rises of necessity: hence comes a cloud, hence water; which again falls, and the earth again becomes wet.[34] Finally, wherever our conclusion is not universally and necessarily true, but true only in most cases, our immediate _principia_ must also be of the same character, true in most cases, but in most cases only.[35]

[Footnote 30: Analyt. Post. II. xii. p. 95, a. 10, 36: [Greek: to\ ga\r me/son o(mo/gonon dei= ei)=nai], &c.]

[Footnote 31: Ibid. a. 24 seq., b. 32; Julius Pacius, ad loc.; Biese, Die Philosophie des Aristot. pp. 302-303.]

[Footnote 32: Analyt. Post. II. xii. p. 95, a. 39-b. 8; Themistius, p. 86.]

[Footnote 33: Analyt. Post. II. xii. p. 95, b. 14-31: [Greek: a)rchê\ de\ kai\ e)n tou/tois a)/mesos lêpte/a].]

[Footnote 34: Ibid. b. 38-p. 96, a**. 7.]

[Footnote 35: Ibid. p. 96, a. 8-19.]

How are we to proceed in hunting out those attributes that are predicated _in Quid_,[36] as belonging to the Essence of the subject? The subject being a lowest species, we must look out for such attributes as belong to all individuals thereof, but which belong also to individuals of other species under the same genus. We shall thus find one, two, three, or more, attributes, each of which, separately taken, belongs to various individuals lying out of the species; but the assemblage of which, collectively taken, does not belong to any individual lying out of the species. The Assemblage thus found is the Essence; and the enunciation thereof is the Definition of the species. Thus, the triad is included in the genus number; in searching for its definition, therefore, we must not go beyond that genus, nor include any attributes (such as _ens_, &c.) predicable of other subjects as well as numbers. Keeping within the limits of the genus, we find that every triad agrees in being an odd number. But this oddness belongs to other numbers also (pentad, heptad, &c.). We therefore look out for other attributes, and we find that every triad agrees in being a prime number, in two distinct senses; first, that it is not measured by any other number; secondly, that it is not compounded of any other numbers. This last attribute belongs to no other odd number except the triad. We have now an assemblage of attributes, which belong each of them to every triad, universally and necessarily, and which, taken all together, belong _exclusively_ to the triad, and therefore constitute its essence or definition. The triad is a number, odd, and prime in the two senses.[37] The _definitum_ and the definition are here exactly co-extensive.

[Footnote 36: Ibid. xiii. p. 96, a. 22: [Greek: pô=s dei= _thêreu/ein_ ta\ e)n tô=| ti/ e)sti katêgorou/mena?]]

[Footnote 37: Analyt. Post. II. xiii. p. 96, a. 24-b. 14. [Greek: ei) toi/nun mêdeni\ u(pa/rchei a)/llô| ê)\ tai=s a)to/mois tria/si, tou=t' a)\n ei)/ê to\ tria/di ei)=nai. u(pokei/sthô ga\r kai\ tou=to, ê( ou)si/a ê( e(ka/stou ei)=nai ê( e)pi\ tai=s a)to/mois e)/schatos toiau/tê katêgori/a. ô(/ste o(moi/ôs kai\ a)/llô| o(tô|ou=n tô=n ou(/tô deichthe/ntôn to\ _au)tô=| ei)=nai_ e)/stai.]]

Where the matter that we study is the entire genus, we must begin by distributing it into its lowest species; _e.g._ number into dyad, triad, &c.; in like manner, taking straight line, circle, right angle, &c.[38] We must first search out the definitions of each of these lowest species; and these having been ascertained, we must next look above the genus, to the Category in which it is itself comprised, whether _Quantum_, _Quale_, &c. Having done thus much we must study the derivative attributes or propria of the lowest species through the common generalities true respecting the larger. We must recollect that these derivative attributes are derived from the essence and definition of the lowest species, the complex flowing from the simple as its _principium_: they belong _per se_ only to the lowest species thus defined; they belong to the higher genera only through those species.[39] It is in this way, and not in any other, that the logical Division of genera, according to specific differences, can be made serviceable for investigation of essential attributes; that is, it can only be made to demonstrate what is derivative from the essence. We have shown already that it cannot help in demonstrating essence or Definition itself. We learn to marshal in proper order the two constituent elements of our definition, and to attach each specific difference to the genus to which it properly belongs. Thus we must not attempt to distribute the genus animal according to the difference of having the wing divided or undivided: many animals will fall under neither of the two heads; the difference in question belongs to the lower genus winged animal, and distributes the same into two species. The characteristic or specific difference must be enunciated and postulated by itself, and must be attached to its appropriate genus in order to form the definition. It is only by careful attention to the steps of legitimate logical Division that we can make sure of including all the particulars and leaving out none.[40]

[Footnote 38: Ibid. b. 18. The straight line is the first or lowest of all lines: no other line can be understood, unless we first understand what is meant by a straight line. In like manner the right angle is the first of all angles, the circle the first of all curvilinear figures (Julius Pacius, ad loc. p. 504).]

[Footnote 39: Analyt. Post. II. xiii. p. 96, b. 19-25: [Greek: meta\ de\ tou=to, la/bo/nta ti/ to\ ge/nos, oi(=on po/teron tô=n posô=n ê)\ tô=n poiô=n, ta\ i)/dia pa/thê theôrei=n dia\ tô=n koinô=n prô/tôn. toi=s ga\r suntitheme/nois e)k tô=n a)to/môn] (speciebus infimis) [Greek: ta\ sumbai/nonta e)k tô=n o(rismô=n e)/stai dê=la, dia\ to\ a)rchê\n ei)=nai pa/ntôn to\n o(rismo/n kai\ to\ a(plou=n, kai\ toi=s a(ploi=s kath' au(ta\ u(pa/rchein ta\ sumbai/nonta mo/nois, toi=s d' a)/llois kat' e)kei=na.]

Themistius illustrates this obscure passage, p. 89. The definitions of [Greek: eu)thei=a grammê/, keklasme/nê grammê/, peripherê\s grammê/], must each of them contain the definition of [Greek: grammê/ (= mê=kos a)plate/s)], since it is in the Category [Greek: Poso/n (poso\n mê=kos a)plate/s)]. But the derivative properties of the circle ([Greek: peripherê\s grammê/]) are deduced from the definition of a circle, and belong to it in the first instance _quâ_ [Greek: peripherê\s grammê/], in a secondary way _quâ_ [Greek: grammê/].]

[Footnote 40: Analyt. Post. II. xiii. p. 96, b. 25-p. 97, a. 6.]

Some contemporaries of Aristotle, and among them Speusippus, maintained that it was impossible either to define, or to divide logically, unless you knew all particulars without exception. You cannot (they said) know any one thing, except by knowing its differences from all other things; which would imply that you knew also all these other things.[41] To these reasoners Aristotle replies: It is not necessary to know _all_ the differences of every thing; you know a thing as soon as you know its essence, with the properties _per se_ which are derivative therefrom. There are many differences not belonging to the essence, but distinguishing from each other two things having the same essence: you may know the thing, without knowing these accidental differences.[42] When you divide a genus into two species, distinguished by one proximate specific difference, such that there cannot be any thing that does not fall under one or other of these _membra condividentia_, and when you have traced the subject investigated under one or other of these members, you can always follow this road until no lower specific difference can be found, and you have then the final essence and definition of the subject; even though you may not know how many _other_ subjects each of the two members may include.[43] Thus does Aristotle reply to Speusippus, showing that it is not necessary, for the definition of one thing, that you should know _all_ other things. His reply, as in many other cases, is founded on the distinction between the Essential and the Accidental.

[Footnote 41: Ibid. p. 97, a. 6-10; Themistius, p. 92. Aristotle does not here expressly name Speusippus, but simply says [Greek: phasi/ tines]. It is Themistius who names Speusippus; and one of the Scholiasts refers to Eudemus as having expressly indicated Speusippus (Schol. p. 248, a. 24, Br.).]

[Footnote 42: Analyt. Post. II. xiii. p. 97, a. 12: [Greek: pollai\ ga\r diaphorai\ u(pa/rchousi toi=s au)toi=s tô=| ei)/dei, a)ll' ou) kat' ou)si/an ou)de\ kath' au(ta/.]]

[Footnote 43: Ibid. a. 18-22: [Greek: phanero\n ga\r o(/ti a)\n ou(/tô badi/zôn e)/lthê| ei)s tau=ta ô(=n mêke/ti e)sti\ diaphora/, e(/xei to\n lo/gon tê=s ou)si/as.]]

To obtain or put together a definition through logical Division, three points are to be attended to.[44] Collect the predicates _in Quid_; range them in the proper order; make sure that there are no more, or that you have collected all. The essential predicates are genera, to be obtained not otherwise than by the method (dialectical) used in concluding accidents. As regards order, you begin with the highest genus, that which is predicable of all the others, while none of these is predicable of it, determining in like fashion the succession of the rest respectively. The collection will be complete, if you divide the highest genus by an exhaustive specific difference, such that every thing must be included in one or other of the two proximate and opposed portions; and then taking the species thus found as your _dividendum_, subdivide it until no lower specific difference can be found, or you obtain from the elements an exact equivalent to the subject.[45]

[Footnote 44: Ibid. a. 23: [Greek: ei)s de\ to\ kataskeua/zein o(/ron dia\ diaire/seôn]. The Scholiast, p. 248, a. 41, explains [Greek: kataskeua/zein] by [Greek: eu(rei=n, sunthei=nai, a)podou=nai]. He distinguishes it from [Greek: a)podeiknu/nai]; demonstration of the definition being impracticable.]

[Footnote 45: Analyt. Post. II. xiii. p. 97, a. 23 seq. See Waitz, Comm. p. 418.]

When the investigation must proceed by getting together a group of similar particulars, you compare them, and note what is the same in all; then turn to another group which are the same _in genere_ yet differ _in specie_ from the first group, and have a different point of community among themselves. You next compare the point of community among the members of the first group, and that among the members of the second group. If the two points of community can be brought under one rational formula, that will be the definition of the subject; but if at the end of the process, the distinct points of community are not found resolvable into any final one, this proves that the supposed _definiendum_ is not one but two or more.[46] For example, suppose you are investigating, What is the essence or definition of magnanimity? You must study various magnanimous individuals, and note what they have in common _quâ_ magnanimous.[47] Thus, Achilles, Ajax, Alkibiades were all magnanimous. Now, that which the three had in common was, that they could not endure to be insulted; on that account Alkibiades went to war with his countrymen, Achilles was angry and stood aloof from the Greeks, Ajax slew himself. But, again, you find two other magnanimous men, Sokrates and Lysander. These two had in common the quality, that they maintained an equal and unshaken temper both in prosperity and adversity. Now when you have got thus far, the question to be examined is, What is the point of identity between the temper that will not endure insult, and the temper that remains undisturbed under all diversities of fortune? If an identity can be found, this will be the essence or definition of magnanimity; to which will belong equanimity as one variety, and intolerance of insult as another. If, on the contrary, no identity can be found, you will then have two distinct mental dispositions, without any common definition.[48]

[Footnote 46: Analyt. Post. II. xiii. p. 97, b. 7-15. [Greek: pa/lin skopei=n ei) tau)to\n e(/ôs a)\n ei)s e(/na e)/lthê| lo/gon; ou(=tos ga\r e)/stai tou= pra/gmatos o(rismo/s. e)a\n de\ mê\ badi/zê| ei)s e(/na a)ll' ei)s du/o ê)\ plei/ô, dê=lon o(/ti ou)k a)\n ei)/ê e(/n ti ei)=nai to\ zêtou/menon, a)lla\ plei/ô.]]

[Footnote 47: Ibid. b. 16: [Greek: skepte/on e)pi/ tinôn megalopsu/chôn, ou(\s i)/smen, ti/ e)/chousin e(\n pa/ntes ê(=| _toiou=toi_.]]

[Footnote 48: Ibid. b. 17-25. [Greek: tau=ta du/o labô\n skopô= ti/ to\ au)to\ e)/chousin ê(/ te a)pa/theia ê( peri\ ta\s tu/chas kai\ ê( mê\ u(pomonê\ a)timazome/nôn. ei) de\ mêde/n, du/o ei)/dê a)\n ei)/ê tê=s megalopsuchi/as.]

Æquam memento rebus in arduis
Servare mentem: non secus in bonis
Ab insolenti temperatam
Lætitiâ.--Horace. _Ode_, ii. 3.

Aristotle says that there will be two species of magnanimity. But surely if the two so-called species connote nothing in common they are not rightly called species, nor is magnanimity rightly called a genus. Equanimity would be distinct from magnanimity; Sokrates and Lysander would not properly be magnanimous but equanimous.]

Every definition must be an universal proposition, applicable, not exclusively to one particular object, but to a class of greater or less extent. The lowest species is easier to define than the higher genus; this is one reason why we must begin with particulars, and ascend to universals. It is in the higher genera that equivocal terms most frequently escape detection.[49] When you are demonstrating, what you have first to attend to is, the completeness of the form of syllogizing: when you are defining, the main requisite is to be perspicuous and intelligible; _i.e._ to avoid equivocal or metaphorical terms.[50] You will best succeed in avoiding them, if you begin with the individuals, or with examples of the lowest species, and then proceed to consider not their resemblances generally, but their resemblances in certain definite ways, as in colour or figure. These more definite resemblances you will note first; upon each you will found a formula of separate definition; after which you will ascend to the more general formula of less definite resemblance common to both. Thus, in regard to the acute or sharp, you will consider the acute in sound, and in other matters (tastes, pains, weapons, angles, &c.), and you will investigate what is the common point of identity characterizing all. Perhaps there may be no such identity; the transfer of the term from one to the other may be only a metaphor: you will thus learn that no common definition is attainable. This is an important lesson; for as we are forbidden to carry on a dialectical debate in metaphorical terms, much more are we forbidden to introduce metaphorical terms in a definition.[51]

[Footnote 49: Analyt. Post. II. xiii. p. 97, b. 29: [Greek: kai\ ga\r ai( o(mônumi/ai **lantha/nousi ma=llon e)n toi=s katho/lou ê)\ e)n toi=s a)diapho/rois.]]

[Footnote 50: Analyt. Post. II. xiii. p. 97, b. 31: [Greek: ô(/sper de e)n tai=s a)podei/xesi dei= to/ ge sullelogi/sthai u(pa/rchein, ou(/tô kai\ e)n toi=s o(/rois _to\ saphe/s_.]

By [Greek: to\ saphe/s], he evidently means the avoidance of equivocal or metaphorical terms, and the adherence to true genera and species. Compare Biese, Die Philosophie des Aristot. pp. 308-310.]

[Footnote 51: Analyt. Post. II. xiii. p. 97, b. 35-39.--([Greek: diale/gesthai/ phêsi, to\ dialektikô=s o(milei=n].--Schol. p. 248, b. 23, Brand.). Aristotle considers it metaphorical when the term _acute_ is applied both to a sound and to an angle.

The treatment of this portion of the Aristotelian doctrine by Prantl (Geschichte der Logik, vol. I. ch. iv. pp. 246, 247, 338), is instructive. He brings out, in peculiar but forcible terms, the idea of "notional causality" which underlies Aristotle's Logic. "So also ist die Definition das Aussprechen _des schöpferischen Wesensbegriffes_. . . . . Soweit der schöpferische Wesensbegriff erreicht werden kann, ist durch denselben die begriffliche Causalität erkannt; und die Einsicht in diese _primitive Ursächlichkeit_ wird in dem Syllogismus vermittelst des Mittelbegriffes erreicht. Ueber den schöpferischen Wesensbegriff hinauszugehen, ist nicht möglich. . . . . Sobald die Definition mehr als eine blosse Namenserklärung ist--und sie muss mehr seyn--erkennt sie den Mittelbegriff als schöpferische Causalität. . . . . Die ontologische Bedeutung des Mittelbegriffes ist, dass er schöpferischer Wesensbegriff ist." Rassow (pp. 51, 63, &c.) adopts a like metaphorical phrase:--"Definitionem est, explicare notionem; quæ quidem est _creatrix rerum causa_."]

To obtain and enunciate correctly the problems suitable for discussion in each branch of science, you must have before you tables of dissection and logical division, and take them as guides;[52] beginning with the highest genus and proceeding downward through the successively descending scale of sub-genera and species. If you are studying animals, you first collect the predicates belonging to all animals; you then take the highest subdivision of the genus animal, such as bird, and you collect the predicates belonging to all birds; and so on to the next in the descending scale. You will be able to show cause why any of these predicates must belong to the man Sokrates, or to the horse Bukephalus; because it belongs to the genus animal, which includes man and horse. Animal will be the middle term in the demonstration.[53] This example is taken from the class-terms current in vulgar speech. But you must not confine yourself to these; you must look out for new classes, bound together by the possession of some common attribute, yet not usually talked of as classes, and you must see whether other attributes can be found constantly conjoined therewith. Thus you find that all animals having horns, have also a structure of stomach fit for rumination, and teeth upon one jaw only. You know, therefore, what is the cause that oxen and sheep have a structure of stomach fit for rumination. It is because they have horns. Having-horns is the middle term of the demonstration.[54] Cases may also be found in which several objects possess no common nature or attribute to bind them into a class, but are yet linked together, by analogy, in different ways, to one and the same common term.[55] Some predicates will be found to accompany constantly this analogy, or to belong to all the objects _quâ_ analogous, just as if they had one and the same class-nature. Demonstration may be applied to these, as to the former cases.

[Footnote 52: Analyt. Post. II. xiv. p. 98**, a. 1. [Greek: pro\s de\ to\ e)/chein ta\ problê/mata, le/gein dei= ta/s te _a)natoma\s_ kai\ ta\s diaire/seis, ou(/tô de\ diale/gein, u(pothe/menon to\ ge/nos to\ koino\n a(pa/ntôn.] This is Waitz's text, which differs from Julius Pacius and from Firmin Didot.

Themistius (pp. 94-95) explains [Greek: ta\s a)natoma\s] to be anatomical drawings or exercises prepared by Aristotle for teaching: [Greek: kai\ ta\s a)natoma\s e)/chein dei= prochei/rôs, o(/sai pepoi/êntai A)ristote/lei].

The collection of Problems or questions for investigation was much prosecuted, not merely by Aristotle but by Theophrastus (Schol. p. 249, a. 12, Br.).]

[Footnote 53: Analyt. Post. II. xiv. p. 98, a. 5-12.]

[Footnote 54: Ibid. a. 13-19. Aristotle assumes that the material which ought to have served for the upper teeth, is appropriated by Nature for the formation of horns.]

[Footnote 55: Ibid. a. 20-23: [Greek: e)/ti d' a)/llos tro/pos e)sti\ _kata\ to\ a)na/logon_ e)kle/gein]. He gives as examples, [Greek: sê/pion, a)/kantha, o)stou=n].]

Problems must be considered to be the same, when the middle term of the demonstration is the same for each, or when the middle term in the one is a subordinate or corollary to that in the other. Thus, the cause of echo, the cause of images in a mirror, the cause of the rainbow, all come under the same general head or middle term (refraction), though with a specific difference in each case. Again, when we investigate the problem, Why does the Nile flow with a more powerful current in the last half of the (lunar) month? the reason is that the month is then more wintry. But why _is_ the month then more wintry? Because the light of the moon is then diminishing. Here are two middle terms, the one of which depends upon the other. The problem for investigation is therefore the same in both.[56]

[Footnote 56: Analyt. Post. II. xv. p. 98, a. 24-34. Theophrastus is said to have made collections of "_like problems_," problems of which the solution depended upon the same middle term (Schol. p. 249, a. 11**, Brand.).]

Respecting _Causa_ and _Causatum_ question may be made whether it is necessary that when the _causatum_ exists, the _causa_ must exist also? The answer must be in the affirmative, if you include the cause in the definition of _causatum_. Thus, if you include in the definition of a lunar eclipse, the cause thereof, viz., intervention of the earth between moon and sun--then, whenever an eclipse occurs, such intervention must occur also. But it must not be supposed that there is here a perfect reciprocation, and that as the _causatum_ is in this case demonstrable from the cause, so there is the like demonstration of the cause from the _causatum_. Such a demonstration is never a demonstration of [Greek: dio/ti]; it is only a demonstration of [Greek: o(/ti]. The _causatum_ is not included in the definition of the cause; if you demonstrate that because the moon is eclipsed, therefore the earth is interposed between the moon and the sun, you prove the fact of the interposition, but you learn nothing about the cause thereof. Again, in a syllogism the middle term is the cause of the conclusion (_i.e._, it is the reason why the major term is predicated of the minor, which predication is the conclusion); and in this sense the cause and _causatum_ may sometimes reciprocate, so that either may be proved by means of the other. But the _causatum_ here reciprocates with the _causa_ only as premiss and conclusion (_i.e._, we may know either by means of the other), not as cause and effect; the _causatum_ is not cause of the _causa_ as a fact and reality, as the _causa_ is cause of the _causatum_.[57]

[Footnote 57: Analyt. Post. II. xvi. p. 98, a. 35, seq. Themistius, pp. 96-97: [Greek: ou) ga/r e)stin ai)/tion tou= tê\n gê=n e)n me/sô| ei)=nai to\ tê\n selê/nên e)klei/pein, a)lla\ me/son tou= sullogismou=; kai\ tou= sumpera/smatos i)/sôs ai)/tion, _tou= pra/gmatos de\ ou)damô=s_.] Themistius here speaks with a precision which is not always present to the mind of Aristotle; for he discriminates the cause of _the fact_ from the cause of the _affirmed fact_ or _conclusion_. M. Barthélemy St. Hilaire says (Plan Général des Derniers Analytiques, p. cxl.):--"Ainsi, la démonstration de l'effet par la cause apprend pourquoi la chose est; la démonstration par l'effet apprend seulement que la chose est. On sait que la terre s'interpose, mais on ne sait pas pourquoi elle s'interpose: et ce qui le montre bien, c'est que l'idée de l'interposition de la terre est indispensable à la définition essentielle de l'éclipse tandis que l'idée de l'éclipse n'a que faire dans la définition de l'interposition. L'interposition de la terre fait donc comprendre l'éclipse; tandis que l'éclipse ne fait pas du tout comprendre l'interposition de la terre."]