Do we not see that the fishes in the sea, when they stretch out their fins and swim about, do always appear larger than their real natural size? And oars too, even though they are very straight, look as if they were broken when they are under water; and things at a great distance display false appearances to our eyes, and in this way do frequently deceive the mind.
Section 183
For at times inanimate objects have been imagined to be alive, and on the contrary living animals have been considered to be lifeless; sometimes again stationary things appear to be in motion, and things in motion appear to be standing still: even things which are approaching towards us do sometimes appear to be retreating from us, and things which are going away do on the other hand appear to be approaching. At times very short things seem to be exceedingly long, and things which have many angles appear to be circular. There is also an infinite number of other things of which a false impression is given though they are open to the sight, which however no man in his senses would subscribe to as certain.
Section 184
What again are we to say of the quantities occurring in things compounded? For it is through the admixture of a greater or a lesser quantity that great injury or good is often done, as in many other instances, so most especially in the case of medicines compounded by medical science.
Section 185
For quantity in such compounds is measured by fixed limits and rules, and it is not safe either to stop short before one has reached them, nor to advance beyond them. For if too little be applied, it relaxes, and if too much, it strains the natural powers; and each extremity is mischievous, the one from its impotence being capable of producing any effect at all, and the other by reason of its exceeding strength being necessarily hurtful. Again it is very plain with reference to smoothness, and roughness, and thickness, and close compression, or on the other hand leanness and slackness, how very much influence all these differences have in respect of doing good or harm.
Section 186
Nor indeed is any one ignorant that scarcely anything whatever of existing things, if you consider it in itself and by itself, is accurately understood; but by comparing it with its opposite, then we arrive at a knowledge of its true nature. As for instance, we comprehend what is meant by little by placing it in juxta-position with what is great; we understand what dry is by comparing it with wet, cold by comparing it with heat, light by comparing it with heavy, black by contrasting it with white, weak by contrasting it with strong, and few by comparing it with many. In the same way also, in whatever is referred to virtue or to vice,
Section 187
what is advantageous is recognised by a comparison with what is injurious, what is beautiful by a comparison with what is unseemly, what is just and generally good, by placing it in juxta-position with what is unjust and bad. And, indeed, if any one considers everything that there is in the world, he will be able to arrive at a proper estimate of its character, by taking it in the same manner; for each separate thing is by itself incomprehensible, but by a comparison with another thing, is easy to understand it.
Section 188
Now, that which is unable to bear witness to itself, but which stands in need of the advocacy of something else, is not to be trusted or thought steady. So that in this way those men are convicted who say that they have no difficulty in assenting to or denying propositions about anything.
Section 189
And why need we wonder? For any one who advances far into matters, and who contemplates them in an unmixed state will know this, that nothing is ever presented to our view according to its real plain nature, but that everything has the most various possible mixtures and combinations.
Section 190
Some one will say, We at once comprehend colours. How so? Do we not do so by means of the external things, air and light, and also by the moisture which exists in our eyes themselves? And in what way are sweet and bitter comprehended? Is it apart from the moisture in our mouths? And as to all the flavours which are in accordance with, or at variance with nature, are not they in the same case? What, again, are we to say of the smells arising from perfumes which are burnt? Do they exhibit plain unmixed simple natures, or rather qualities compounded of themselves and of the air, and sometimes also of the fire which consumes their bodies, and also of the faculty existing in our own nostrils?
Section 191
From all this we collect the inference that we have neither any proper comprehension of colours, not only of the combination which consists of the objects submitted to our view and of light; nor of smells, but only of the mixture which consists of that which flows from substances and the all-receiving air; nor of tastes, but only of the union which arises from the tasteable object presented to us, and the moist substance in our mouths.
Section 192
Since, then, this is the state of affairs with respect to these matters, it is worth while to appreciate correctly the simplicity, or rashness, or impudence of those who pretend to be able with ease to form an opinion, so as to assent to or deny what is stated with respect to anything whatever. For if the simple faculties are wanting, but the mingled powers and those which are formed by contributions from many sources are within sight, and if it is impossible for those which are invisible to be seen, and if we are unable to comprehend separately the character of all the component parts which are united to make up each faculty, then what remains except that we must think it necessary to suspend our judgment?
Section 193
And then, too, do not those facts which are diffused over nearly the whole world, and which have caused both to Greeks and barbarians such erroneous judgments, exhort us not to be too ready in giving our credence to what is not seen? And what are these facts? Surely they are the instructions which we have received from our childhood, and our national customs and ancient laws, of which it is admitted that there is not a single one which is of equal force among all people; but it is notorious that they vary according to the different countries, and nations, and cities, aye, and even still more, in every village and private house, and even with respect to men, and women, and infant children, in almost every point.
Section 194
At all events, what are accounted disgraceful actions among us, are by others looked upon as honourable; what we think becoming, others call unseemly; what we pronounce just, others renounce as iniquitous; others think our holy actions impious, our lawful deeds lawless: and further, what we think praiseworthy, they find fault with; what we think worthy of all honour, is, in the eyes of others, deserving of punishment; and, in fact, they think most things to be of a contrary character to what we think.