XLVI. (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? (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.

XLVII. (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? (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. (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. (195) And why need I be prolix and dwell further on this subject, when I am called off by other more important points? If then, any one, leaving out of the question all other more remarkable subjects of speculation, were to choose to devote his time to an investigation of the subject here proposed, namely, to examine the education, and customs, and laws of every different nation, and country, and place, and city; of all subjects and rulers; of all men, whether renowned or inglorious, whether free or slaves, whether ignorant or endowed with knowledge, he would spend not one day or two, nor a month, nor even a year, but his whole life, even though he were to reach a great age, in the investigation; and he would nevertheless still leave a vast number of subjects unexamined, uninvestigated, and unmentioned, without perceiving it. (196) Therefore, since there are some persons and things removed from other persons and things, not by a short distance only, but since they are utterly different, it then follows of necessity that the perceptions which occur to men of different things must also differ, and that their opinions must be at variance with one another.