Chapter III (2)

[Footnote 40: The remarks of Ritter (Gesch. der Philos. ii. p. 189. 2nd ed.) upon these Megaric philosophers are more just and discerning than those made by most of the historians of philosophy "Doch darf man wohl annehmen, dass sie solche Trugschlüsse nicht zur Täuschung,** sondern zur Belehrung für unvorsichtige, oder zur Warnung vor der Seichtigkeit gewöhnlicher Vorstellungsweisen, gebrauchen wollten. So viel ist gewiss, dass die Megariker sich viel mit den Formen des Denken beschäftigten, vielleicht mehr zu Aufsuchung einzelner Regeln, als zur Begründung eines wissenschaftlichen Zusammenhangs unter ihnen; obwohl auch besondere Theile der Logik unter ihren Schriften erwähnt werden."

This is much more reasonable than the language of Prantl, who denounces "the shamelessness of doctrinarism" (die Unverschämtheit des Doctrinarismus) belonging to these Megarici "the petulance and vanity which prompted them to seek celebrity by intentional offences against sound common sense," &c. (Gesch. der Logik, pp. 39-40.--Sir Wm. Hamilton has some good remarks on these sophisms, in his Lectures on Logic, Lect. xxiii. p. 452 seq.)]

[Footnote 41: See the first chapter of his book v. on Fallacies, System of Logic, vol. ii.]

[Footnote 42: Aristotel. Metaphys. B. 1, p. 995, a. 33.

[Greek: dio\ dei= ta\s duscherei/as tetheôrêke/nai pa/sas pro/teron, tou/tôn de\ cha/rin kai\ dia\ to\ tou\s zêtou=ntas a)/neu tou= diaporê=sai prô=ton o(moi/ous ei)=nai toi=s poi= dei= badi/zein a)gnoou=si, kai\ pro\s tou/tois ou)d' ei) pote to\ zêtou/menon eu(/rêken ê)\ mê\ gignô/skein; to\ ga\r te/los tou/tô| me\n ou) dê=lon, tô=| de\ proêporêko/ti dê=lon].

Aristotle devotes the whole of this Book to an enumeration of [Greek: a)po/riai].]

[Side-note: If the process of theorising be admissible, it must include negative as well as affirmative.]

You may dislike philosophy: you may undervalue, or altogether proscribe, the process of theorising. This is the standing-point usual with the bulk of mankind, ancient as well as modern: who generally dislike all accurate reasoning, or analysis and discrimination of familiar abstract words, as mean and tiresome hair-splitting.[43] But if you admit the business of theorising to be legitimate, useful, and even honourable, you must reckon on free working of independent, individual, minds as the operative force--and on the necessity of dissentient, conflicting, manifestations of this common force, as essential conditions to any successful result. Upon no other conditions can you obtain any tolerable body of reasoned truth--or even reasoned _quasi-truth_.

[Footnote 43: See my account of the Platonic dialogue Hippias Major, vol. ii. chap. xiii. Aristot. Metaphys. A. minor, p. 995, a. 9. [Greek: tou\s de\ lupei= to\ a)kribe\s, ê)\ dia\ to\ mê\ du/nasthai sunei/rein, ê)\ dia\ tê\n mikrologi/an; e)/chei ga/r ti to\ a)kribe\s toiou=ton, ô(/ste katha/per e)pi\ tô=n sumbolai/ôn, kai\ e)pi\ tô=n lo/gôn a)neleu/theron ei)=nai tisi dokei=]. Cicero (Paradoxa, c. 2) talks of the "minutæ interrogatiunculæ" of the Stoics as tedious and tiresome.]

[Side-note: Logical position of the Megaric philosophers erroneously described by historians of philosophy. Necessity of a complete collection of difficulties.]

Now the historians of philosophy seldom take this view of philosophy as a whole--as a field to which the free antithesis of affirmative and negative is indispensable. They consider true philosophy as represented by Sokrates, Plato, and Aristotle, one or other of them: while the contemporaries of these eminent men are discredited under the name of Sophists, Eristics, or sham-philosophers, sowing tares among the legitimate crop of wheat--or as devils whom the miraculous virtue of Sokrates and Plato is employed in expelling from the Athenian mind. Even the companions of Sokrates, and the Megarics among them, whom we know only upon the imperfect testimony of opponents, have fallen under this unmerited sentence:[44] as if they were destructive agents breaking down an edifice of well-constituted philosophy--no such edifice in fact having ever existed in Greece, though there were several dissenting lecture rooms and conflicting veins of speculation promoted by eminent individuals.

[Footnote 44: The same charge is put by Cicero into the mouth of Lucullus against the Academics: "Similiter vos (Academici) quum perturbare, ut illi" (the Gracchi and others) "rempublicam, sic vos philosophiam, benè jam constitutam velitis. . . . Tum exortus est, ut in optimâ republicâ Tib. Gracchus, qui otium perturbaret, sic Arcesilas, qui constitutam philosophiam everteret" (Acad. Prior, ii. 5, 14-15).

Even in the liberal and comprehensive history of the Greek philosophy by Zeller (vol. ii. p. 187, ed. 2nd), respecting Eukleides' and the Megarians;--"Dagegen bot der _Streit gegen die geltenden Meinungen_ dem Scharfsinn, der Rechthaberei, und dem wissenschaftlichen Ehrgeiz, ein unerschöpfliches Feld dar, welches denn auch die Megarischen Philosophen rüstig ausbeuteten."

If by "die geltenden Meinungen" Zeller means the common sense of the day that is, the opinions and beliefs current among the [Greek: i)diô=tai], the working, enjoying, non-theorising public--it is very true that the Megaric philosophers contended against them: but Sokrates and Plato contended against them quite as much: we see this in the Platonic Apology, Gorgias, Republic, Timæus, Parmenidês, &c.

If, on the other hand, by "die geltenden Meinungen" Zeller means any philosophical or logical theories generally or universally admitted by thinking men as valid, the answer is that there were none such in the fourth and third centuries B.C. Various eminent speculative individuals were labouring to construct such theories, each in his own way, and each with a certain congregation of partisans; but established theory there was none. Nor can any theory (whether accepted or not) be firm or trustworthy, unless it be exposed to the continued thrusts of the negative weapon, searching out its vulnerable points. We know of the Megarics only what they furnished towards that negative testing; without which, however,--as we may learn from Plato and Aristotle themselves,--the true value of the affirmative defences can never be measured.]

Whoever undertakes, _bonâ fide_, to frame a complete and defensible logical theory, will desire to have before him a copious collection of such difficulties, and will consider those who propound them as useful auxiliaries.[45] If he finds no one to propound them, he will have to imagine them for himself. "The philosophy of reasoning" (observes Mr. John Stuart Mill) "must comprise the philosophy of bad as well as of good reasoning."[46] The one cannot be complete without the other. To enumerate the different varieties of apparent evidence which is not real evidence (called Fallacies), and of apparent contradictions which are not real contradictions--referred as far as may be to classes, each illustrated by a suitable type--is among the duties of a logician. He will find this duty much facilitated, if there happen to exist around him an active habit of dialectic debate: ingenious men who really study the modes of puzzling and confuting a well-armed adversary, as well as of defending themselves against the like. Such a habit did exist at Athens: and unless it had existed, the Aristotelian theories on logic would probably never have been framed. Contemporary and antecedent dialecticians, the Megarici among them, supplied the stock of particular examples enumerated and criticised by Aristotle in the Topica:[47] which treatise (especially the last book, De Sophisticis Elenchis) is intended both to explain the theory, and to give suggestions on the practice, of logical controversy. A man who takes lessons in fencing must learn not only how to thrust and parry, but also how to impose on his opponent by feints, and to meet the feints employed against himself: a general who learns the art of war must know how to take advantage of the enemy by effective cheating and treachery (to use the language of Xenophon), and how to avoid being cheated himself. The Aristotelian Topica, in like manner, teach the arts both of dialectic attack and of dialectic defence.[48]

[Footnote 45: Marbach (Gesch. der Philos. s. 91), though he treats the Megarics as jesters (which I do not think they were), yet adds very justly: "Nevertheless these puzzles (propounded by the Megarics) have their serious and scientific side. We are forced to inquire, how it happens that the contradictions shown up in them are not merely possible but even necessary."

Both Tiedemann and Winckelmann also remark that the debaters called Eristics contributed greatly to the formation of the theory and precepts of Logic, afterwards laid out by Aristotle. Winckelmann, Prolegg. ad Platon. Euthydem. pp. xxiv.-xxxi. Even Stallbaum, though full of harshness towards those Sophists whom he describes as belonging to the school of Protagoras, treats the Megaric philosophers with much greater respect. Prolegom. ad Platon. Euthydem. p. 9.]

[Footnote 46: System of Logic, Book v. 1, 1.]

[Footnote 47: Prantl (Gesch. der Logik, vol. i. pp. 43-50) ascribes to the Megarics all or nearly all the sophisms which Aristotle notices in the Treatise De Sophisticis Elenchis. This is more than can be proved, and more than I think probable. Several of them are taken from the Platonic Euthydêmus.]

[Footnote 48: See the remarkable passages in the discourses of Sokrates (Memorab. iii. 1, 6; iv. 2, 15), and in that of Kambyses to Cyrus, which repeats the same opinion--Cyropæd. i. 6, 27--respecting the amount of deceit, treachery, the thievish and rapacious qualities required for conducting war against an enemy--([Greek: ta\ pro\s tou\s polemi/ous no/mima], i. 6, 34).

Aristotle treats of Dialectic, as he does of Rhetoric, as an art having its theory, and precepts founded upon that theory. I shall have occasion to observe in a future chapter (xxi.), that logical Fallacies are not generated or invented by persons called Sophists, but are inherent liabilities to error in the human intellect; and that the habit of debate affords the only means of bringing them into clear daylight, and guarding against being deceived by them. Aristotle gives precepts both how to thrust, and how to parry with the best effect: if he had taught only how to parry, he would have left out one-half of the art.

One of the most learned and candid of the Aristotelian commentators--M. Barthélemy St. Hilaire--observes as follows (Logique d'Aristote, p. 435, Paris, 1838) respecting De Sophist. Elenchis:--

"Aristote va donc s'occuper de la marche qu'il faut donner aux discussions sophistiques: et ici il serait difficile quelquefois de décider, à la manière dont les choses sont présentées par lui, si ce sont des conseils qu'il donne aux Sophistes, ou à ceux qui veulent éviter leurs ruses. Tout ce qui précède, prouve, au reste, que c'est en ce dernier sens qu'il faut entendre la pensée du philosophe. Ceci est d'ailleurs la seconde portion du traîté."

It appears to me that Aristotle intended to teach or to suggest both the two things which are here placed in Antithesis--though I do not agree with M. St. Hilaire's way of putting the alternative--as if there were one class of persons, professional Sophists, who fenced with poisoned weapons, while every one except them refrained from such weapons. Aristotle intends to teach the art of Dialectic as a whole; he neither intends nor wishes that any learners shall make a bad use of his teaching; but if they do use it badly, the fault does not lie with him. See the observations in the beginning of the Rhetorica, i. p. 1355, a. 26, and the observations put by Plato into the mouth of Gorgias (Gorg. p. 456 E).

Even in the Analytica Priora (ii. 19, a. 34) (independent of the Topica) Aristotle says:--[Greek: chrê\ d' o(/per phula/ttesthai paragge/llomen a)pokrinome/nous, au)tou\s e)picheirou=ntas peira=sthtai lantha/nein]. Investigations of the double or triple senses of words (he says) are useful--[Greek: kai\ pro\s to\ mê\ paralogisthê=nai, kai\ pro\s to\ paralogi/sasthai], Topica, i. 18, p. 108, a. 26. See also other passages of the Topica where artifices are indicated for the purpose of concealing your own plan of proceeding and inducing your opponent to make answer in the sense which you wish, Topica, i. 2, p. 101, a. 25; vi. 10, p. 148, a. 37; viii. 1, p. 151, b. 23; viii. 1, p. 153, a. 6; viii. 2, p. 154, a. 5; viii. 11, p. 161, a. 24 seq. You must be provided with the means of meeting every sort and variety of objection--[Greek: pro\s ga\r to\n pa/ntôs e)nista/menon pa/ntôs a)ntitakte/on e)sti/n]. Topic. v. 4, p. 134, a. 4.

I shall again have to touch on the Topica, in this point of view, as founded upon and illustrating the Megaric logical puzzles (ch. viii. of the present volume).]

[Side-note: Sophisms propounded by Eubulides. 1. Mentiens. 2. The Veiled Man. 3. Sorites. 4. Cornutus.]

The Sophisms ascribed to Eubulidês, looked at from the point of view of logical theory, deserve that attention which they seem to have received. The logician lays down as a rule that no affirmative proposition can be at the same time true and false. Now the first sophism (called _Mentiens_) exhibits the case of a proposition which is, or appears to be, at the same time true and false.[49] It is for the logician to explain how this proposition can be brought under his rule--or else to admit it as an exception. Again, the second sophism in the list (the Veiled or Hidden Man) is so contrived as to involve the respondent in a contradiction: he is made to say both that he knows his father, and that he does not know his father. Both the one answer and the other follow naturally from the questions and circumstances supposed. The contradiction points to the loose and equivocal way in which the word _to know_ is used in common speech. Such equivocal meaning of words is not only one of the frequent sources of error and fallacy in reasoning, but also one of the least heeded by persons untrained in dialectics; who are apt to presume that the same word bears always the same meaning. To guard against this cause of error, and to determine (or impel others to determine) the accurate meaning or various distinct meanings of each word, is among the duties of the logician: and I will add that the verb _to know_ stands high in the list of words requiring such determination--as the Platonic Theætêtus[50] alone would be sufficient to teach us. Farthermore, when we examine what is called the Soritês of Eubulides, we perceive that it brings to view an inherent indeterminateness of various terms: indeterminateness which cannot be avoided, but which must be pointed out in order that it may not mislead. You cannot say how many grains are _much_--or how many grains make _a heap_. When this want of precision, pervading many words in the language, was first brought to notice in a suitable special case, it would naturally appear a striking novelty. Lastly, the sophism called [Greek: Kerati/nês] or Cornutus, is one of great plausibility, which would probably impose upon most persons, if the question were asked for the first time without any forewarning. It serves to administer a lesson, nowise unprofitable or superfluous, that before you answer a question, you should fully weigh its import and its collateral bearings.

[Footnote 49: Theophrastus wrote a treatise in three books on the solution of the puzzle called [Greek: O( pseudo/menos] (see the list of his lost works in Diogenes L. v. 49). We find also other treatises entitled [Greek: Megariko\s a/] (which Diogenes cites, vi. 22),--[Greek: A)gônistiko\n tê=s peri\ tou\s e)ristikou\s lo/gous theôri/as--Sophisma/tôn a/, b]--besides several more titles relating to dialectics, and bearing upon the solution of syllogistic problems. Chrysippus also, in the ensuing century, wrote a treatise in three books, [Greek: Peri\ tê=s tou= pseudome/non lu/seôs] (Diog. vii. 107). Such facts show the importance of these problems in their bearing upon logical theory, as conceived by the ancient world. Epikurus also wrote against the [Greek: Megarikoi/] (Diog. x. 27).

The discussion of sophisms, or logical difficulties ([Greek: lu/seis a)pori/ôn]), was a favourite occupation at the banquets of philosophers at Athens, on or about 100 B.C. [Greek: A)nti/patros d' o( philo/sophos, sumpo/sio/n pote suna/gôn, sune/taxe toi=s e)rchome/nois ô(s peri\ sophisma/tôn e(rou=sin] (Athenæus, v. 186 C). Plutarch, Non posse suaviter vivi secundum Epicurum, p. 1096 C; De Sanitate Præcepta, c. 20, p. 133 B.]

[Footnote 50: Various portions of the Theætêtus illustrate this Megaric sophism (pp. 165-188). The situation assumed in the question of Eubulidês--having before your eyes a person veiled--might form a suitable addition to the various contingencies specified in Theætêt. pp. 192-193.

The manner in which the Platonic Sokrates proves (Theæt. 165) that you at the same time see, and do not see, an object before you, is quite as sophistical as the way in which Eubulidês proves that you both know, and do not know, your father.]

[Side-note: Causes of error constant--the Megarics were sentinals against them.]

The causes of error and fallacy are inherent in the complication of nature, the imperfection of language, the small range of facts which we know, the indefinite varieties of comparison possible among those facts, and the diverse or opposite predispositions, intellectual as well as emotional, of individual minds. They are not fabricated by those who first draw attention to them.[51] The Megarics, far from being themselves deceivers, served as sentinels against deceit. They planted conspicuous beacons upon some of the sunken rocks whereon unwary reasoners were likely to be wrecked. When the general type of a fallacy is illustrated by a particular case in which the conclusion is manifestly untrue, the like fallacy is rendered less operative for the future.

[Footnote 51: Cicero, in his Academ. Prior, ii. 92-94, has very just remarks on the obscurities and difficulties in the reasoning process, which the Megarics and others brought to view--and were blamed for so doing, as unfair and captious reasoners--as if they had themselves created the difficulties--"(Dialectica) primo progressu festivé tradit elementa loquendi et ambiguorum intelligentiam concludendique rationem; tum paucis additis venit ad soritas, lubricum sané et periculosum locum, quod tu modo dicebas esse vitiosum interrogandi genus. Quid ergo? _istius vitii num nostra culpa est_? Rerum natura nullam nobis dedit cognitionem finium, ut ullâ in re statuere possimus quatenus. Nec hoc in acervo tritici solum, unde nomen est, sed nullâ omnino in re minutatim interroganti--dives, pauper--clarus, obscurus, sit--multa, pauca, magna, parva, longa, brevia, lata, angusta, quanto aut addito aut dempto certum respondeamus, non habemus. At vitiosi sunt soritæ. Frangite igitur eos, si potestis, ne molesti sint. . . Sic me (inquit) sustineo, neque diutius captiosé interroganti respondes. Si habes quod liqueat neque respondes, superbis: si non habes, ne tu quidem percipis."

The principle of the Sorites ([Greek: ê( sôritikê\ a)pori/a]--Sextus adv. Gramm. s. 68), though differently applied, is involved in the argument of Zeno the Eleate, addressed to Protagoras--see Simplikius ad Aristot. Physic. 250, p. 423, b. 42. Sch. Brand. Compare chap. ii. of this volume.]

[Side-note: Controversy of the Megarics with Aristotle about Power. Arguments of Aristotle.]

Of the positive doctrines of the Megarics we know little: but there is one upon which Aristotle enters into controversy with them, and upon which (as far as can be made out) I think they were in the right. In the question about Power, they held that the power to do a thing did not exist, except when the thing was actually done: that an architect, for example, had no power to build a house, except when he actually did build one. Aristotle controverts this opinion at some length; contending that there exists a sort of power or cause which is in itself irregular and indeterminate, sometimes turning to the affirmative, sometimes to the negative, to do or not to do;[52] that the architect _has_ the _power to build_ constantly, though he exerts it only on occasion: and that many absurdities would follow if we did not admit, That a given power or energy--and the exercise of that power--are things distinct and separable.[53]

[Footnote 52: Aristot. De Interpret. p. 19, a. 6-20. [Greek: o(/lôs e)/stin e)n toi=s mê\ a)ei\ e)nergou=si to\ dunato\n ei)=nai kai\ mê\ o(moi/ôs; e)n oi(=s a)mphô e)nde/chetai, kai\ to\ ei)=nai kai\ to\ mê\ ei)=nai, ô(/ste kai\ to\ gene/sthai kai\ to\ mê\ gene/sthai.]]

[Footnote 53: Aristot. Metaph. [Greek: Th]. 3, p. 1046, b. 29. [Greek: Ei)si\ de/ tines, oi)/ phasin, oi(=on oi( Megarikoi/, o(/tan e)nergê=|, mo/non du/nasthai, o(/tan de\ mê\ e)nergê=|, mê\ du/nasthai--oi(=on to\n mê\ oi)kodomou=nta ou) du/nasthai oi)kodomei=n, a)lla\ to\n oi)kodomou=nta o(/tan oi)kodomê=|; o(moi/ôs de\ kai\ e)pi\ tô=n a)/llôn].

Deycks (De Megaricorum Doctrinâ, pp. 70-71) considers this opinion of the Megarics to be derived from their general Eleatic theory of the Ens Unum et Immotum. But I see no logical connection between the two.]

[Side-note: These arguments not valid against the Megarici.]

Now these arguments of Aristotle are by no means valid against the Megarics, whose doctrine, though apparently paradoxical, will appear when explained to be no paradox at all, but perfectly true. When we say that the architect has power to build, we do not mean that he has power to do so under all supposable circumstances, but only under certain conditions: we wish to distinguish him from non-professional men, who under those same conditions have no power to build. The architect must be awake and sober: he must have the will or disposition to build:[54] he must be provided with tools and materials, and be secure against destroying enemies. These and other conditions being generally understood, it is unnecessary to enunciate them in common speech. But when we engage in dialectic analysis, the accurate discussion ([Greek: a)kribologi/a]) indispensable to philosophy requires us to bring under distinct notice, that which the elliptical character of common speech implies without enunciating. Unless these favourable conditions be supposed, the architect is no more able to build than an ordinary non-professional man. Now the Megarics did not deny the distinctive character of the architect, as compared with the non-architect: but they defined more accurately in what it consisted, by restoring the omitted conditions. They went a step farther: they pointed out that whenever the architect finds himself in concert with these accompanying conditions (his own volition being one of the conditions) he goes to work--and the building is produced. As the house is not built, unless he wills to build, and has tools and materials, &c.--so conversely, whenever he has the will to build and has tools and materials, &c., the house is actually built. The effect is not produced, except when the full assemblage of antecedent conditions come together: but as soon as they do come together, the effect is assuredly produced. The accomplishments of the architect, though an essential item, are yet only one item among several, of the conditions necessary to building the house. He has no power to build, except when those other conditions are assumed along with him: in other words, he has no such power except when he actually does build.

[Footnote 54: About this condition implied in the predicate [Greek: dunato/s], see Plato, Hippias Minor, p. 366 D.]

[Side-note: His arguments cited and criticised.]

Aristotle urges against the Megarics various arguments, as follows:--1. Their doctrine implies that the architect is not an architect, and does not possess his professional skill,[55] except at the moment when he is actually building.--But the Megarics would have denied that their doctrine did imply this. The architect possesses his art at all times: but his art does not constitute a power of building except under certain accompanying conditions.

[Footnote 55: Aristot. Metaph. [Greek: Th]. 3, 1047, a. 3. [Greek: o(/tan pau/sêtai (oi)kodomô=n) ou)ch e(/xei tê\n te/chnên.]]

2. The Megaric doctrine is the same as that of Protagoras, implying that there exists no perceivable Object, and no Subject capable of perceiving, except at the moment when perception actually takes place.[56] On this we may observe, that the Megarics coincide with Protagoras thus far, that they bring into open daylight the relative and conditional, which the received phraseology tends to hide. But neither they nor he affirm what is here put upon them. When we speak of a perceivable Object, we mean that which may and will be perceived, _if_ there be a proper Subject to perceive it: when we affirm a Subject capable of perception, we mean, one which will perceive, under those circumstances which we call the presence of an Object suitably placed. The Subject and Object are correlates: but it is convenient to have a language in which one of them alone is introduced unconditionally, while the conditional sign is applied to the correlate: though the matter affirmed involves a condition common to both.

[Footnote 56: Aristot. Metaph. [Greek: Th]. 3, 1047, a. 8-13.]

3. According to the Megaric doctrine (Aristotle argues) every man when not actually seeing, is blind; every man when not actually speaking, is dumb.--Here the Megarics would have said that this is a misinterpretation of the terms dumb and blind; which denote a person who cannot speak or see, even though he wishes it. One who is now silent, though not dumb, may speak if he wills it: but his own volition is an essential condition.[57]

[Footnote 57: The question between Aristotle and the Megarics has not passed out of debate with modern philosophers.

Dr. Thomas Brown observes, in his inquiry into Cause and Effect--"From the mere silence of any one, we cannot infer that he is dumb in consequence of organic imperfection. He may be silent only because he has no desire of speaking, not because speech would not have followed his desire: and it is not with the mere _existence_ of any one, but _with his desire of speaking_, that we suppose utterance to be connected. A man who has _no desire of speaking, has in truth_, and in strictness of language, _no power of speaking, when in that state of mind_: since he has not a circumstance which, as immediately prior, is essential to speech. But since he has that power, as soon as the new circumstance of desire arises--and as the presence or absence of the desire cannot be perceived but in its effects--_there is no inconvenience in the common language_, which ascribes the power, _as if it were possessed at all times, and in all circumstances of mind_, though unquestionably, nothing more is meant than that the desire existing will be followed by utterance." (Brown, Essay on the Relation of Cause and Effect, p. 200.)

This is the real sense of what Aristotle calls [Greek: to\ de\ (le/getai) dunato/n, oi(=on dunato\n ei)=nai badi/zein o(/ti badiseien a)\n], _i.e._ he will walk _if_ he desires to do so (De Interpret. p. 23, a. 9-15).]

4. According to the Megaric doctrine (says Aristotle) when you are now lying down, you have no power to rise: when you are standing up, you have no power to lie down: so that the present condition of affairs must continue for ever unchanged: nothing can come into existence which is not now in being.--Here again, the Megarics would have denied his inference. The man who is now standing up, has power to lie down, _if he wills_ to do so--or he may be thrown down by a superior force: that is, he will lie down, _if_ some new fact of a certain character shall supervene. The Megarics do not deny that he has power, _if_--so and so: they deny that he has power, without the _if_--that is, without the farther accompaniments essential to energy.

[Side-note: Potential as distinguished from the Actual--What it is.]

On the whole, it seems to me that Aristotle's refutation of the Megarics is unsuccessful. A given assemblage of conditions is requisite for the production of any act: while there are other circumstances, which, if present at the same time, would defeat its production. We often find it convenient to describe a state of things in which some of the antecedent conditions are present without the rest: in which therefore the act is not produced, yet would be produced, if the remaining circumstances were present, and if the opposing circumstances were absent.[58] The state of things thus described is the _potential_ as distinguished from the _actual_: power, distinguished from act or energy: it represents an incomplete assemblage of the antecedent positive conditions--or perhaps a complete assemblage, but counteracted by some opposing circumstances. As soon as the assemblage becomes complete, and the opposing circumstances removed, the potential passes into the actual. The architect, when he is not building, possesses, not indeed the full or plenary power to build, but an important fraction of that power, which will become plenary when the other fractions supervene, but will then at the same time become operative, so as to produce the actual building.[59]

[Footnote 58: Hobbes, in his Computation or Logic (chaps. ix. and x. Of Cause and Effect. Of Power and Act) expounds this subject with his usual perspicuity.

"A Cause simply, or an Entire Cause, is the aggregate of all the accidents, both of the agents, how many soever they be, and of the patient, put together; which, when they are all supposed to be present, it cannot be understood but that the effect is produced at the same instant: and if any one of them be wanting, it cannot be understood but that the effect is not produced" (ix. 3).

"Correspondent to Cause and Effect are Power and Act: nay, those and these are the same things, though for divers considerations they have divers names. For whensoever any agent has all those accidents which are necessarily requisite for the production of some effect in the patient, then we say that agent has power to produce that effect if it be applied to a patient. In like manner, whensoever any patient has all those accidents which it is requisite it should have for the production of some effect in it, we say it is in the power of that patient to produce that effect if it be applied to a fitting agent. Power, active and passive, are parts only of plenary and entire power: nor, except they be joined, can any effect proceed from them. And therefore these powers are but conditional: namely, the agent has power if it be applied to a patient, and the patient has power if it be applied to an agent. _Otherwise neither of them have power, nor can the accidents which are in them severally be properly called powers_: nor any action be said to be possible for the power of the agent alone or the patient alone."]

[Footnote 59: Aristotle does in fact grant all that is here said, in the same book and in the page next subsequent to that which contains his arguments against the Megaric doctrine, Metaphys. [Greek: Th]. 5, 1048, a. 1-24.

In this chapter Aristotle distinguishes powers belonging to things, from powers belonging to persons--powers irrational from powers rational--powers in which the agent acts without any will or choice, from those in which the will or choice of the agent is one item of the aggregate of conditions. He here expressly recognises that the power of the agent, separately considered, is only _conditional_; that is, conditional on the presence and suitable state of the patient, as well as upon the absence of counteracting circumstances. But he contends that such absence of counteracting circumstances is plainly implied, and need not be expressly mentioned in the definition.

[Greek: e)pei\ de\ to\ dunato\n ti\ dunato\n kai\ pote\ kai\ pô=s kai\ o(/sa a)/lla a)na/gkê prosei=nai e)n tô=| diorismô=|--

to\ dunato\n kata\ lo/gon a(/pan a)na/gkê, o(/tan o)re/gêtai, ou)= t' e)/chei tê\n du/namin kai\ ô(s e)/chei, tou=to poiei=n; e)/chei de\ paro/ntos tou= pathêtikou= kai\ ô(di\ e)/chontos poiei=n; _ei) de\ mê/, poiei=n ou) dunê/setai_. to\ ga\r mêtheno\s tô=n e(/xô kôlu/ontos prosdiori/zesthai, ou)the\n e)/ti dei=; tê\n ga\r du/namin e)/chei ô(/s e)/sti du/namis tou= poiei=n, _e)/sti d' ou) pa/ntôs_, a)ll' e)cho/ntôn pô=s, e)n oi(=s a)phoristhê/setai kai\ ta\ e(/xô kôlu/onta; a)phairei=tai ga\r tau=ta tô=n e)n tô=| diorismô=| proso/ntôn e)/nia]. The commentary of Alexander Aphr. upon this chapter is well worth consulting (pp. 546-548 of the edition of his commentary by Bonitz, 1847). Moreover Aristotle affirms in this chapter, that when [Greek: to\ poiêtiko\n] and [Greek: to\ pathêtiko\n] come together under suitable circumstances, the power will certainly pass into act.

Here then, it seems to me, Aristotle concedes the doctrine which the Megarics affirmed; or, if there be any difference between them, it is rather verbal than real. In fact, Aristotle's reasoning in the third chapter (wherein he impugns the doctrine of the Megarics), and the definition of [Greek: dunato\n] which he gives in that chapter (1047, a. 25), are hardly to be reconciled with his reasoning in the fifth chapter. Bonitz (Notes on the Metaphys. pp. 393-395) complains of the _mira levitas_ of Aristotle in his reasoning against the Megarics, and of his omitting to distinguish between _Vermögen_ and _Möglichkeit_. I will not use so uncourteous a phrase; but I think his refutation of the Megarics is both unsatisfactory and contradicted by himself. I agree with the following remark of Bonitz:--"Nec mirum, quod Megarici, aliis illi quidem in rebus arguti, in hâc autem satis acuti, existentiam [Greek: tô=| duna/mei o)/nti] tribuere recusarint," &c.]

[Side-note: Diodôrus Kronus--his doctrine about [Greek: to\ dunato/n].]

The doctrine which I have just been canvassing is expressly cited by Aristotle as a Megaric doctrine, and was therefore probably held by his contemporary Eubulidês. From the pains which Aristotle takes (in the 'De Interpretatione' and elsewhere) to explain and vindicate his own doctrine about the Potential and the Actual, we may see that it was a theme much debated among the dialecticians of the day. And we read of another Megaric, Diodorus[60] Kronus, perhaps contemporary (yet probably a little later than Aristotle), as advancing a position substantially the same as that of Eubulidês. That alone is possible (Diodorus affirmed) which either is happening now, or will happen at some future time. As in speaking about facts of an unrecorded past, we know well that a given fact either occurred or did not occur, yet without knowing which of the two is true--and therefore we affirm only that the fact _may_ have occurred: so also about the future, either the assertion that a given fact will at some time occur, is positively true, or the assertion that it will never occur, is positively true: the assertion that it may or may not occur some time or other, represents only our ignorance, which of the two is true. That which will never at any time occur, is impossible.

[Footnote 60: The dialectic ingenuity of Diodorus is powerfully attested by the verse of Ariston, applied to describe Arkesilaus (Sextus Emp. Pyrrh. Hyp. i. p. 234):

[Greek: Pro/sthe Pla/tôn, o)/pithen Pu/r)r(ôn, me/ssos Dio/dôros.]]

[Side-note: Sophism of Diodorus--[Greek: O( Kurieu/ôn].]

The argument here recited must have been older than Diodorus, since Aristotle states and controverts it: but it seems to have been handled by him in a peculiar dialectic arrangement, which obtained the title of [Greek: O( Kurieu/ôn].[61] The Stoics (especially Chrysippus), in times somewhat later, impugned the opinion of Diodorus, though seemingly upon grounds not quite the same as Aristotle. This problem was one upon which speculative minds occupied themselves for several centuries. Aristotle and Chrysippus maintained that affirmations respecting the past were _necessary_ (one necessarily true and the other necessarily false)--affirmations respecting the future, _contingent_ (one must be true and the other false, but either might be true). Diodorus held that both varieties of affirmations were equally necessary--Kleanthes the Stoic thought that both were equally contingent.[62]

[Footnote 61: Aristot. De Interpret. p. 18, a. pp. 27-38. Alexander ad Aristot. Analyt. Prior. 34, p. 163, b. 34, Schol. Brandis. See also Sir William Hamilton's Lectures on Logic, Lect. xxiii. p. 464.]

[Footnote 62: Arrian ad Epiktet. ii. p. 19. Upton, in his notes on this passage of Arrian (p. 151) has embodied a very valuable and elaborate commentary by Mr. James Harris (the great English Aristotelian scholar of the 18th century), explaining the nature of this controversy, and the argument called [Greek: o( Kurieu/ôn].

Compare Cicero, De Fato, c. 7-9. Epistol. Fam. ix. 4.]

It was thus that the Megaric dialecticians, with that fertility of mind which belonged to the Platonic and Aristotelian century, stirred up many real problems and difficulties connected with logical evidence, and supplied matters for discussion which not only occupied the speculative minds of the next four or five centuries, but have continued in debate down to the present day.

[Side-note: Question between Aristotle and Diodôrus depends upon whether universal regularity of sequence be admitted or denied.]

The question about the Possible and Impossible, raised between Aristotle and Diodorus, depends upon the larger question, Whether there are universal laws of Nature or not? whether the sequences are, universally and throughout, composed of assemblages of conditions regularly antecedent, and assemblages of events regularly consequent; though from the number and complication of causes, partly co-operating and partly conflicting with each other, we with our limited intelligence are often unable to predict the course of events in each particular situation. Sokrates, Plato, and Aristotle, all maintained that regular sequence of antecedent and consequent was not universal, but partial only:[63] that there were some agencies essentially regular, in which observation of the past afforded ground for predicting the future--other agencies (or the same agencies on different occasions) essentially irregular, in which the observation of the past afforded no such ground. Aristotle admitted a graduation of causes from perfect regularity to perfect irregularity:--1. The Celestial Spheres, with their included bodies or divine persons, which revolved and exercised a great and preponderant influence throughout the Kosmos, with perfect uniformity; having no power of contraries, _i.e._, having no power of doing anything else but what they actually did (having [Greek: e)nergei/a] without [Greek: du/namis]). 2. The four Elements, in which the natural agencies were to a great degree necessary and uniform, but also in a certain degree otherwise--either always or for the most part uniform ([Greek: to\ ô(s e)pi\ to\ polu/])--tending by inherent appetency towards uniformity, but not always attaining it. 3. Besides these there were two other varieties of Causes accidental, or perfectly irregular--Chance and Spontaneity: powers of contraries, or with equal chance of contrary manifestations--essentially capricious, undeterminable, unpredictable.[64] This _Chance_ of Aristotle--with one of two contraries sure to turn up, though you could never tell beforehand which of the two--was a conception analogous to what logicians sometimes call an Indefinite Proposition, or to what some grammarians have reckoned as a special variety of genders called the _doubtful gender_. There were thus positive causes of regularity, and positive causes of irregularity, the co-operation or conflict of which gave the total manifestations of the actual universe. The principle of irregularity, or the Indeterminate, is sometimes described under the name of Matter,[65] as distinguishable from, yet co-operating with, the three determinate Causes--Formal, Efficient, Final. The Potential--the Indeterminate--the _May or May not be_--is characterised by Aristotle as one of the inherent principles operative in the Kosmos.

[Footnote 63: Xenophon, Memor. i. 1; Plato, Timæus, p. 48 A. [Greek: ê( planôme/nê ai)ti/a], &c.]

[Footnote 64: [Greek: Ê( tu/chê--to\ o(po/ter' e)/tuche--to\ au)to/maton] are in the conception of Aristotle independent [Greek: A)rchai/], attached to and blending with [Greek: a)na/gkê] and [Greek: to\ ô(s e)pi\ to\ polu/]. See Physic. ii. 196, b. 11; Metaphys. E. 1026-1027.

Sometimes [Greek: to\ o(po/ter' e)/tuche] is spoken of as an [Greek: A)rchê/], but not as an [Greek: ai)/tion], or belonging to [Greek: u(/lê] as the [Greek: A)rchê/]. 1027, b. 11. [Greek: dê=lon a)/ra o(/ti me/chri tino\s badi/zei a)rchê=s, au)/tê d' ou)/keti ei)s a)/llo; e)/stai ou)=n ê( tou= o(po/ter' e)/tuchen au)/tê, kai\ ai)/tioi tê=s gene/seôs au)tê=s ou)the/n].

See, respecting the different notions of Cause held by ancient philosophers, my remarks on the Platonic Phædon infrà, vol. iii.** ch. xxv.]

[Footnote 65: Aristot. Metaph. E. 1027, a. 13; A. 1071, a. 10.

[Greek: ô(/ste ê( u(/lê e)/stai ai)ti/a, ê( e)ndechome/n ê para\ to\ ô(s e)pi\ to polu\ a)/llôs tou= sumbebêko/tos].

Matter is represented as the principle of irregularity, of [Greek: to\ o(po/ter' e)/tuche]--as the [Greek: du/namis tô=n e)nanti/ôn].

In the explanation given by Alexander of Aphrodisias of the Peripatetic doctrine respecting chance--free-will, the principle of irregularity--[Greek: tu/chê] is no longer assigned to the material cause, but is treated as an [Greek: ai)ti/a kata\ sumbebêko/s], distinguished from [Greek: ai)ti/a proêgou/mena] or [Greek: kath' au(ta/]. The exposition given of the doctrine by Alexander is valuable and interesting. See his treatise De Fato, addressed to the Emperor Severus, in the edition of Orelli, Zurich. 1824 (a very useful volume, containing treatises of Ammonius, Plotinus, Bardesanes, &c., on the same subject); also several sections of his Quæstiones Naturales et Morales, ed. Spengel, Munich, 1842, pp. 22-61-65-123, &c. He gives, however, a different explanation of [Greek: to\ dunato\n] and [Greek: to\ a)du/naton] in pp. 62-63, which would not be at variance with the doctrine of Diodorus. We may remark that Alexander puts the antithesis of the two doctrines differently from Aristotle,--in this way. 1. Either all events happen [Greek: kath' ei(marme/nên]. 2. Or all events do not happen [Greek: kath' ei(marme/nên], but some events are [Greek: e)ph' ê(mi=n]. See De Fato, p. 14 seq. This way of putting the question is directed more against the Stoics, who were the great advocates of [Greek: ei(marme/nê], than against the Megaric Diodorus. The treatises of Chrysippus and the other Stoics alter both the wording and the putting of the thesis. We know that Chrysippus impugned the doctrine of Diodorus, but I do not see how.

The Stoic antithesis of [Greek: ta kath' ei(marme/nên--ta\ e)ph' ê(mi=n] is different from the antithesis conceived by Aristotle and does not touch the question about the universality of regular sequence. [Greek: Ta\ e)ph' ê(mi=n] describes those sequences in which human volition forms one among the appreciable conditions determining or modifying the result; [Greek: ta\ kath' ei(marme/nên] includes all the other sequences wherein human volition has no appreciable influence. But the sequence [Greek: tô=n e)ph' ê(mi=n] is just as regular as the sequence [Greek: tô=n kath' ei(marme/nên]: both the one and the other are often imperfectly predictable, because our knowledge of facts and power of comparison is so imperfect.

Theophrastus discussed [Greek: to\ kath' ei(marme/nên], and explained it to mean the same as [Greek: to\ kata\ phu/sin. phanerô/tata de\ Theo/phrastos dei/knusi tau)to\n o(\n to\ kath' ei(marme/nên tô=| kata\ phu/sin] (Alexander Aphrodisias ad Aristot. De Animâ, ii.).]

[Side-note: Conclusion of Diodôrus--defended by Hobbes--Explanation given by Hobbes.]

In what manner Diodorus stated and defended his opinion upon this point, we have no information. We know only that he placed affirmations respecting the future on the same footing as affirmations respecting the past: maintaining that our potential affirmation--_May or May not be_--respecting some future event, meant no more than it means respecting some past event, viz.: no inherent indeterminateness in the future sequence, but our ignorance of the determining conditions, and our inability to calculate their combined working.[66] In regard to scientific method generally, this problem is of the highest importance: for it is only so far as uniformity of sequence prevails, that facts become fit matter for scientific study.[67] Consistently with the doctrine of all-pervading uniformity of sequence, the definition of Hobbes gives the only complete account of the Impossible and Possible: _i.e._ an account such as would appear to an omniscient calculator, where _May or May not_ merge in _Will or Will not_. According as each person falls short of or approaches this ideal standard--according to his knowledge and mental resource, inductive and deductive--will be his appreciation of what may be or may not be--as of what may have been or may not have been during the past. But such appreciation, being relative to each individual mind, is liable to vary indefinitely, and does not admit of being embodied in one general definition.

[Footnote 66: The same doctrine as that of the Megaric Diodorus is declared by Hobbes in clear and explicit language (First Grounds of Philosophy, ii. 10, 4-5):--"That is an impossible act, for the production of which there is no power plenary. For seeing plenary power is that in which all things concur which are requisite for the production of an act,** if the power shall never be plenary, there will always be wanting some of those things, without which the act cannot be produced. Wherefore that act shall never be produced: that is, that act is _impossible_. And every act, which is not impossible, is _possible_. Every act therefore which is possible, shall at some time or other be produced. For if it shall never be produced, then those things shall never concur which are requisite for the production of it; wherefore the act is _impossible_, by the definition; which is contrary to what was supposed.

"A _necessary act_ is that, the production of which it is impossible to hinder: and therefore every act that shall be produced, shall necessarily be produced; for that it shall not be produced is impossible, because, as has already been demonstrated, every possible act shall at some time be produced. Nay, this proposition--_What shall be shall be_--is as necessary a proposition as this--_A man is a man_.

"But here, perhaps, some man will ask whether those future things which are commonly called _contingents_, are necessary. I say, then, that generally all contingents have their necessary causes, but are called _contingents_, in respect of other events on which they do not depend--as the rain which shall be to-morrow shall be necessary, that is, from necessary causes; but we think and say, it happens by chance, because we do not yet perceive the causes thereof, though they exist now. For men commonly call that _casual_ or _contingent_, whereof they do not perceive the necessary cause: _and in the same manner they use to speak of things past, when not knowing whether a thing be done or not, they say, It is possible it never was done._

"Wherefore all propositions concerning future things, contingent or not contingent, as this--It will rain to-morrow, or To-morrow the sun will rise--are either necessarily true or necessarily false: but we call them contingent, because we do not yet know whether they be true or false; whereas their verity depends not upon our knowledge, but upon the foregoing of their causes. But there are some, who, though they will confess this whole proposition--_ To-morrow it will either rain or not rain_--to be true, yet they will not acknowledge the parts of it, as, _To-morrow it will rain_, or _To-morrow it will not rain_, to be either of them true by itself; because (they say) neither this nor that is true _determinately_. But what is this _true determinately_, but true _upon our knowledge_ or _evidently true_? And therefore they say no more but that it is not yet known whether it be true or not; but they say it more obscurely, and darken the evidence of the truth with the same words by which they endeavour to hide their own ignorance."]

[Footnote 67: The reader will find this problem admirably handled in Mr. John Stuart Mill's System of Logic, Book iii. ch. 21, and Book vi. chs. 2 and 8; also in the volume of Professor Bain on the Emotions and the Will, Chapter on Belief.]

Besides the above doctrine respecting Possible and Impossible, there is also ascribed to Diodorus a doctrine respecting Hypothetical Propositions, which, as far as I comprehend it, appears to have been a correct one.[68] He is also said to have reasoned against the reality of motion, renewing the arguments of Zeno the Eleate.

[Footnote 68: Sextus Emp. Pyrrhon. Hypotyp. ii. pp. 110-115. [Greek: a)lêthe\s sunêmme/non]. Adv. Mathemat. viii. 112. Philo maintained that an hypothetical proposition was true, if both the antecedent and consequent were true--"If it be day, I am conversing". Diodorus denied that this proposition, as an Hypothetical proposition, was true: since the consequent might be false, though the antecedent were true. An Hypothetical proposition was true only when, assuming the antecedent to be true, the consequent must be true also.]

[Side-note: Reasonings of Diodôrus--respecting Hypothetical Propositions--respecting Motion. His difficulties about the _Now_ of time.]

But if he reproduced the arguments of Zeno, he also employed another, peculiar to himself. He admitted the reality of _past_ motion: but he denied the reality of _present_ motion. You may affirm truly (he said) that a thing _has been moved_: but you cannot truly affirm that any thing _is being moved_. Since it was _here_ before, and is _there_ now, you may be sure that it has been moved: but actual present motion you cannot perceive or prove. Affirmation in the perfect tense may be true, when affirmation in the present tense neither is nor ever was true: thus it is true to say--Helen _had_ three husbands (Menelaus, Paris, Deiphobus): but it was never true to say--Helen _has_ three husbands, since they became her husbands in succession.[69] Diodorus supported this paradox by some ingenious arguments, and the opinion which he denied seems to have presented itself to him as involving the position of indivisible minima--atoms of body, points of space, instants of time. He admitted such minima of atoms, but not of space or time: and without such admission he could not make intelligible to himself the fact of present or actual motion. He could find no present _Now_ or Minimum of Time; without which neither could any present motion be found. Plato in the Parmenidês[70] professes to have found this inexplicable moment of transition, but he describes it in terms not likely to satisfy a dialectical mind: and Aristotle denying that the Now is any portion or constituent part of time, considers it only as a boundary of the past and future.[71]

[Footnote 69: Sextus Empir. adv. Mathemat. x. pp. 85-101.]

[Footnote 70: Plato, Parmenidês, p. 156 D-E. [Greek: Po/t' ou)=n, metaba/llei? ou)/te ga\r e(sto\s a)\n ou)/te kenou/menon meta/balloi, ou)/te e)n chro/nô| o)/n]. (Here Plato adverts to the difficulties attending the supposition of actual [Greek: metabolê/], as Diodorus to those of actual [Greek: ki/nêsis]. Next we have Plato's hypothesis for getting over the difficulties.) [Greek: A)=r' ou)=n e)sti/ to\ a)/topon tou=to, e)n ô)=| to/t' a)\n ei)/ê o(/te metaba/llei? To\ poi=on dê/? _To\ e)xai/phnês; ê( e)xai/phnês au)/tê phu/sis a)/topos_ tis e)gka/thêtai metaxu\ tê=s kinê/seôs te kai\ sta/seôs, e)n chro/nô| ou)deni\ ou)=sa, kai\ ei)s tau/tên dê\ kai\ e)k tau/tês to/ te kinou/menon metaba/llei e)pi\ to\ e)sta/nai kai\ to\ e)sto\s e)pi\ to\ kinei=sthai].

Diodorus could not make out this [Greek: phu/sis a)/topos] which Plato calls [Greek: to\ e)xai/phnês].]

[Footnote 71: To illustrate this apparent paradox of Diodorus, affirming past motion, but denying present motion, we may compare what is said by Aristotle about the Now or Point of Present Time--that it is not a part, but a boundary between Past and Future.

Aristot. Physic. iv. p. 218, a. 4-10. [Greek: tou= de\ chro/non ta\ me\n ge/gone, ta\ de\ me/llei, e)sti d' ou)de\n, o)/ntos meristou=; to\ de\ nu=n ou) me/ros--to\ de\ nu=n pe/ras e)/sti] (a. 24)--p. 222, a. 10-20-223, a. 20. [Greek: o( de\ chro/nos kai\ ê( ki/nêsis a(/ma kata/ te du/namin kai\ kat' e)nergei/an].

Which doctrine is thus rendered by Harris in his Hermes, ch. vii. pp. 101-103-105:--"Both Points and Nows being taken as Bounds, and not as Parts, it will follow that in the same manner as the same point may be the end of one line and the beginning of another--so the same Now may be the End of one time, and the beginning of another. . . I say of these two times, that with respect to the _Now_, or Instant which they include, the first of them is necessarily Past time, as being previous to it: the other is necessarily Future, as being subsequent. . . From the above speculations, there follow some conclusions, which may be called paradoxes, till they have been attentively considered. In the first place, there cannot (strictly speaking) be any such thing as Time Present. For if all Time be transient, as well as continuous, it cannot like a line be present altogether, but part will necessarily be gone and part be coming. If therefore any portion of its continuity were to be present at once, it would so far quit its transient nature, and be Time no longer. But if no portion of its continuity can be thus present, how can Time possibly be present, to which such continuity is essential?"--Compare Sir William Hamilton's Discussions on Philosophy, p. 581.]

[Side-note: Motion is always present, past, and future.]

This opinion of Aristotle is in the main consonant with that of Diodorus; who, when he denied the reality of present motion, meant probably only to deny the reality of _present motion apart from past and future motion_. Herein also we find him agreeing with Hobbes, who denies the same in clearer language.[72] Sextus Empiricus declares Diodorus to have been inconsistent in admitting past motion while he denied present motion.[73] But this seems not more inconsistent than the doctrine of Aristotle respecting the _Now_ of time. I know, when I compare a child or a young tree with what they respectively were a year ago, that they have grown: but whether they actually are growing, at every moment of the intervening time, is not ascertainable by sense, and is a matter of probable inference only.[74] Diodorus could not understand present motion, except in conjunction with past and future motion, as being the common limit of the two: but he could understand past motion, without reference to present or future. He could not state to himself a satisfactory theory respecting the beginning of motion: as we may see by his reasonings distinguishing the motion of a body all at once in its integrity, from the motion of a body considered as proceeding from the separate motion of its constituent atoms--the moving atoms preponderating over the atoms at rest, and determining them to motion,[75] until gradually the whole body came to move. The same argument re-appears in another example, when he argues--The wall does not fall while its component stones hold together, for then it is still standing: nor yet when they have come apart, for then it _has_ fallen.[76]