_The second Reason, which, if alone, would have been a sufficient one, is, that it is impossible to subject the Treatment of chronical Distempers to the Capacity and Conduct of Persons, who are not Physicians. Each acute Distemper generally arises from one Cause; and the Treatment of it is simple and uniform; since those Symptoms, which manifest the Malady, point out its Cause and Treatment. But the Case is very differently circumstanced in tedious and languid Diseases; each of which may depend on so many and various Causes (and it is only the real, the true Cause, which ought to determine us in selecting its proper Remedies) that though the Distemper and its Appellation are evidently known, a meer By-stander may be very remote from penetrating into its true Cause; and consequently be incapable of chusing the best Medicines for it. It is this precise and distinguishing Discernment of the real particular Cause *[or of the contingent Concurrence of more than one]* that necessarily requires the Presence of Persons conversant in the Study and the Practice of all the Parts of Physick; and which Knowledge it is impossible for People, who are Strangers to such Studies, to arrive at. Moreover, their frequent Complexness; the Variety of their Symptoms; the different Stages of these tedious Diseases [not exactly attended to even by many competent Physicians] the Difficulty of ascertaining the different Doses of Medicines, whose Activity may make the smallest Error highly dangerous, &c. &c. are really such trying Circumstances, as render the fittest Treatment of these Diseases sufficiently difficult and embarrassing to the most experienced Physicians, and unattainable by those who are not Physicians._ _A third Reason is, that, even supposing all these Circumstances might be made so plain and easy, as to be comprehended by every Reader, they would require a Work of an excessive Length; and thence be disproportioned to the Faculties of those, for whom it was intended. One single chronical Disease might require as large a Volume as the present one._ _But finally, were I to acknowledge, that this Compliance was both necessary and practicable, I declare I find it exceeds my Abilities; and that I am also far from having sufficient Leisure for the Execution of it. It is my Wish that others would attempt it, and may succeed in accomplishing it; but I hope these truly worthy Persons, who have honoured me by proposing the Achievement of it to myself, will perceive the Reasons for my not complying with it, in all their Force; and not ascribe a Refusal, which arises from the very Nature of the thing, either to Obstinacy, or to any Want of an Inclination to oblige them._