If we were even assured that, when they make a mistake, that mistake of theirs would do us no harm, though it did us no good, it were a reasonable bargain to venture the making ourselves better without any danger of being made worse.  AEsop tells a story, that one who had bought a Morisco slave, believing that his black complexion had arrived by accident and the ill usage of his former master, caused him to enter with great care into a course of baths and potions:  it happened that the Moor was nothing amended in his tawny complexion, but he wholly lost his former health.  How often do we see physicians impute the death of their patients to one another?  I remember that some years ago there was an epidemical disease, very dangerous and for the most part mortal, that raged in the towns about us:  the storm being over which had swept away an infinite number of men, one of the most famous physicians of all the country, presently after published a book upon that subject, wherein, upon better thoughts, he confesses that the letting blood in that disease was the principal cause of so many mishaps.  Moreover, their authors hold that there is no physic that has not something hurtful in it.  And if even those of the best operation in some measure offend us, what must those do that are totally misapplied?  For my own part, though there were nothing else in the case, I am of opinion, that to those who loathe the taste of physic, it must needs be a dangerous and prejudicial endeavour to force it down at so incommodious a time, and with so much aversion, and believe that it marvellously distempers a sick person at a time when he has so much need of repose.  And more over, if we but consider the occasions upon which they usually ground the cause of our diseases, they are so light and nice, that I thence conclude a very little error in the dispensation of their drugs may do a great deal of mischief.  Now, if the mistake of a physician be so dangerous, we are in but a scurvy condition; for it is almost impossible but he must often fall into those mistakes:  he had need of too many parts, considerations, and circumstances, rightly to level his design:  he must know the sick person’s complexion, his temperament, his humours, inclinations, actions, nay, his very thoughts and imaginations; he must be assured of the external circumstances, of the nature of the place, the quality of the air and season, the situation of the planets, and their influences:  he must know in the disease, the causes, prognostics, affections, and critical days; in the drugs, the weight, the power of working, the country, figure, age, and dispensation, and he must know how rightly to proportion and mix them together, to beget a just and perfect symmetry; wherein if there be the least error, if amongst so many springs there be but any one out of order, ’tis enough to destroy us.  God knows with how great difficulty most of these things are to be understood:  for (for example) how shall the physician find out