Aristotle

“ For of one thing, so far as it is one, there is one science, so that if to know that which is demonstrable be to possess demonstration, an impossibility would happen, for he who possesses definition would know scientifically without demonstration. ”

“ The investigation of the science of Mind, especially as to its element, Thought, is of so interesting a character as in great measure to reconcile the inquirer to the abstruseness of formal reasoning. The beauty of the flower, whilst concealing the ruggedness, is apt to withdraw our attention from the utility, of the soil on which it grows; and thus in like manner the charms of Idealism, ending but too frequently in visionary speculation, have obstructed the clear appreciation of the design and use of Logic. ”

“ If however species be relative, we must see whether genus also is relative, for if species be a relative, genus is also, as in the double and the multiple, for each of these is a relative. If then genus be a relative, it is not requisite that species also should be, for science is of the number of relatives, but grammar is not. Or does what was before asserted appear neither to be true? for virtue is that which is beautiful and which is good, and virtue is a relative, but the good and the beautiful are not relatives, but qualities. ”

“ For of some things knowledge is acquired after this manner, nor is the extreme known through the middle, as such things as are singulars, and are not predicated of any subject. Perhaps however we must confess that we possess knowledge after a certain manner before induction or the assumption of a syllogism, but in another manner not. For what a man is ignorant about its existence at all, how could he know at all that it has two right angles? But it is evident that he thus knows because he knows the universal, but singly he does not know it. ”

“ We sometimes indeed know if it is, accidentally, knowing sometimes something belonging to the thing, as thunder we know, because it is a certain sound of the clouds, and an eclipse, because it is a certain privation of light, and a man, because it is a certain animal, and soul, because it moves itself. ”

“ If, indeed, any one should suppose that to be an elenchus, which is according to equivocation, it will be impossible for the respondent in any way to avoid confutation by an elenchus, for in visible things it is necessary to deny the name which he affirms, and to affirm what he denied. For as some correct there is no benefit, for they say that Coriscus is not musical and unmusical, but that this Coriscus is musical, and that unmusical, since that Coriscus is, will be the same sentence with that this Coriscus is unmusical or musical, which he at one and the same time affirms and denies. ”

“ Yet there is contrariety in relatives, as virtue is contrary to vice, each of them being relative, and knowledge to ignorance; but contrariety is not inherent in all relatives, since there is nothing contrary to double, nor to triple, nor to any thing of the sort.
Relatives appear, notwithstanding, to receive the more and the less, for the like and the unlike are said to be so, more and less, and the equal and the unequal are so called, more and less, each of them being a relative, for the similar is said to be similar to something, and the unequal, unequal to something. ”

“ It is clearly then impossible to possess scientific knowledge of any thing demonstrable by sensible perception, unless some one should affirm that sensible perception is this, to possess science through demonstration. There are indeed certain problems which are referred to the deficiency of our sensible perception, for some if we should see them we should not investigate, not as knowing from seeing, but as possessing the universal from seeing. ”

“ Chapter 1 Of problems, some are universal but others particular, the universal then, as that all pleasure is good, and that no pleasure is good, but the particular, as that a certain pleasure is good, and a certain pleasure is not good. ”

“ We may learn Logic and yet not be able to think; but the science cannot be blamed for the imperfection of the element worked upon, any more than the artificer for the inferiority of the only material within his reach. It is sufficient that Logic, without entering into all the phenomena of mind, provides certain forms which an argument, to be legitimate, must exhibit, certain tests by which fallacy may be detected, and certain barriers against ambiguity in the use of language. ”

“ It is a quaint remark of Erasmus, that the human understanding, like a drunken clown lifted on horseback, falls over on the farther side the instant he is supported on the nearer; and this is the characteristic of human praise and censure. From an ignorant and exaggerated notion of its purport, Logic, instead of being limited to its proper sphere, was supposed commensurate with the whole investigation of abstract truth in relation to matter, cause, and entity,—in fact, the substance of a folio volume, describing every phase of human life, compressed into a few pages of Boethius and Aldrich. ”

“ Examine, likewise, whether the opposite is the genus of the opposite, as if the multiple is the genus of the double, the sub-multiple is so, of the half, for the opposite must necessarily be the genus of the opposite. If, then, any one asserts science to be sense, it will be requisite that the object of science should be sensible, which, however, is not the case, for not every object of science is sensible, as some things intelligible are objects of science. Wherefore, the sensible is not the genus of the object of science, but if it be not, neither is sense, the genus of science. ”

“ Clearly, then, we must not define through such things, but through those that are simply more known, since thus only would one and the same definition be always produced. Perhaps indeed what is simply known is not that which is known to all, but that (which is known) to those who have their intellect well disposed, just as what is simply wholesome is that which is so, to those whose bodies are in a good state. ”

“ It happens also, that the same things are contrary to themselves, since if the "great" be opposed to the "small," but the same thing at the same time be great and small, the same thing would be contrary to itself, but it is amongst the number of impossibilities, that the same thing should be contrary to itself, wherefore the great is not contrary to the small, nor the many to the few, so that even if some one should say that these do not belong to relatives, but to quantity, still they will have no contrary. ”

“ But of thesis, that which receives either part of contradiction, as for instance, I mean that a certain thing is, or that it is not, is hypothesis, but that which is without this, is definition. For definition is a thesis, since the arithmetician lays down unity to be that which is indivisible, according to quantity, yet it is not hypothesis, since what unity is, and that unity is, are not the same thing. ”

“ Chapter 18 It is clear, also, that if any sense be deficient, a certain science must be also deficient, which we cannot possess, since we learn either by induction or by demonstration. Now demonstration is from universals, but induction from particulars, it is impossible however to investigate universals, except through induction, since things which are said to be from abstraction, will be known through induction; if any one desires to make it parent that some things are present with each genus, although they are not separable, so far as each is such a thing. ”

“ For those who suppose that knowledge does not subsist at all, these think that we are to proceed to infinity as if we may not know things subsequent by things prior, of which there are no first, reasoning rightly, since it is impossible to penetrate infinites. And if (they say) we are to stop, and there are principles, these are unknown, since there is no demonstration of them, which alone they say is to know scientifically; but if it is not possible to know first things, neither can we know either simply or properly things which result from these, but by hypothesis, if these exist. ”

“ Or again, as men define night, the shadow of the earth, or an earthquake, the motion of the earth, or a cloud, the condensation of the air, or wind, the motion of the air, for the quantity, quality, the where, and by what, must be added. In like manner, as to other such things, since he who omits any difference whatever, does not state what is the very nature of the thing; indeed we must always argue against what is wanting, for neither will an earthquake be the motion of earth in any manner, nor in any quantity, as neither will wind be the motion of air in any manner, nor in any quantity. ”

“ Contraries, however, evidently are, by their nature, adapted to subsist about the same thing, either in species or genus, since disease and health naturally subsist in the body of an animal, but whiteness and blackness simply in body, and justice and injustice in the soul of man. ”

“ We may however form a judgment of the disposition by the body, if a person grants that whatever passions are natural, change at once the body and the soul, since perhaps one who has learned music has changed his soul in some respect, but this passion is not of those which are natural to us, but such as angers and desires, which belong to natural emotions. If therefore this should be granted, and one thing should be a sign of one (passion) , and we are able to lay hold of the peculiar passion and sign of each genus, we shall be able to conjecture from nature. ”

“ First then we must endeavour to select the two propositions of a syllogism, for it is easier to divide into greater than into less parts, and composites are greater than the things of which they are composed; next we must consider whether it is in a whole or in a part, and if both propositions should not be assumed, oneself placing one of them. For those who propose the universal do not receive the other which is contained in it, neither when they write, nor when they interrogate, or propose these, but omit those by which these are concluded, and question other things to no purpose. ”

“ Notwithstanding, since we must believe in and know a thing from possessing such a syllogism as we call demonstration, and this is, because these are so, of which syllogism consists—it is necessary not only to have a previous knowledge of the first, or all, or some things, but that they should be more known, for that on account of which any thing exists, always exists itself in a greater degree; for example, that on account of which we love is itself more beloved. ”

“ We on the contrary assert, that neither is all science demonstrative, but that the science of things immediate is indemonstrable. And this is evidently necessary, for if it is requisite to know things prior, and from which demonstration subsists, but some time or other there is a stand made at things immediate, these must of necessity be indemonstrable. This therefore we thus assert, and we say that there is not only science, but also a certain principle of science, by which we know terms. ”

“ Therefore, it is possible that he who lays down a thesis, may define according to denomination (the genus as an accident) , e. g. that it is accidental to justice to be a virtue; frequently, however, without definition, it is evident that he has given the genus as an accident, as if any one should have said, that whiteness is coloured, or that walking is moved, for the predication of species is paronymously asserted from no genus, but all genera are predicated of species synonymously, since species receive the name and definition, of genera. ”

“ Chapter 11 "Evil" is of necessity opposed to good, and this is evident from an induction of singulars, as disease to health, and cowardice to courage, and similarly of the rest. But to evil, at one time, good, is contrary, and at another, evil, for to indigence being an evil, excess is contrary, which is also an evil; in like manner, mediocrity, which is a good, is opposed to each of them. A man may perceive this in respect of a few instances, but in the majority the contrary to evil is always good. ”

“ For definition is of what a thing is, and of substance, but all demonstrations appear to suppose and assume what a thing is, as mathematics, what is unity and what an odd number, and the rest in like manner. Moreover every demonstration shows something of somewhat, as that it is, or that it is not, but in definition one thing is not predicated of another, as neither animal of biped, nor this of animal, nor figure of superficies, for superficies is not figure, nor figure superficies. ”

“ Secondary substances signify a certain "quale." but rather they signify a certain quality, for the subject is not one, as the primary substance, but "man" and "animal" are predicated in respect of many. Neither do they signify simply a certain quality, as "white," for "white" signifies nothing else but a thing of a certain quality, but the species and the genus determine the quality, about the substance, for they signify what quality a certain substance possesses: still a wider limit is made by genus than by species, for whoever speaks of "animal," comprehends more than he who speaks of "man." ”

“ Chapter 12 The cause of things which are, is the same also as that of things which are generated, which have been generated, and which will be, for the middle is the cause, except that being is the cause to be, what is generated, to those which are generated, what has been, to those which have been, and what will be to those that will be. Thus why was there an eclipse? because the earth was interposed, but an eclipse is generated, because an interposition of the earth is generated, but there will be, because the earth will be, and there is, because it is interposed. ”

“ This too is common, that when genus or difference is subverted, the things under them are also subverted co-subverted, for as when animal is not, horse is not, nor man, thus also, when rational is not, there will be no animal which uses reason. Now, it is the property of genus to be predicated of more things than difference, species, property, and accident are, for animal (is predicated) of man and horse, bird and snake, but quadruped of animals alone, which have four feet; again, man of individuals alone, and capacity of neighing of horse alone, and of particulars. ”

“ It is also sophistical, when a paradox is laid down, to demand that what is apparent should be answered, that being proposed which seemed true from the beginning, and to question things thus, "Whether does it seem so to you?" for it is necessary if the question be of those things from which a syllogism is formed, that there should be either an elenchus or a paradox; if he grants, an elenchus, but if he neither concedes nor says that it seems to him to be true, something contrary to opinion, and if he does not concede, but acknowledges it seems true to him, a form of elenchus. ”

“ But it is also manifest that we may infer a true conclusion from false premises, as we have observed before, but from opposites we cannot, for a syllogism always arises contrary to the fact, as if a thing is good, (the conclusion will be,) that it is not good, or if it is an animal, that it is not an animal, because the syllogism is from contradiction, and the subject terms are either the same, or the one is a whole, but the other a part. ”