How could they know living in Persia that individually these...

How could they know living in Persia that individually these articles produce no effects? How came they to know the places where these articles are produced, when they are so different in kind and nature, and grow at so great a distance from each other-of some plants roots alone are used, of others the fruit, shell, essence, juice, gum or oil- some are used internally, and others externally; again in different countries they hold different names; the people of different countries are not always friendly to each other they vary in opinions, manners and modes of life; one nation desires to predominate over the other , they slaughter and pillage and try to imprison one another: it is not always easy for a stranger to carryon investigation?

How was that knowledge gained? Can you say that the person who invented the science went to every nook and corner of the world, learnt every language, and traveled every country? That he was able to investigate the medicines from east to west quite fearlessly and safely, and that he never fell sick, did not under go: any troubles but remained healthy and intact?

That he made no mistakes, was never misdirected found all the countries, remembered all he learnt, remained always happy and finished all his researches with regard to the origin and nature and effects of what he sought-despite all differences of color quality and names? That he got correct description of each and every tree, its origin, smell and taste, flowers and fruits?

Can you really think the enterprise such as one individual may undertake and accomplish when you consider that each and every medicine has at least twenty different natures? Is it not impossible that he learnt the science of medicine the secrets of the trees that demand close observation and grow in so many different countries? Even granting him the possibility how did he come by the knowledge that such and such a plant could be used as a medicine for the senses do not hold the innate ideas?

How did he separate the bitter, the sweet, the saltish and acrid trees-one from another? If you say that he did so by inquiry and converse with the people of different lands they grew in how came he to inquire and converse about the things unknown to him? How came it to his mind that he must ask these questions of a particular man? And how could he arrive at a satisfactory conclusion despite so many social and political barriers, and the difference of languages?