there are very few men in the world, to whom I can, with the like sincerity, profess myself to be, as I am,

Dear sir,

Your most real friend, and

very humble and obliged servant,

THO, MOLYNEUX.

SIR,

Mr. Locke to Dr. Molyneux.

Oates, Nov. 1, 1692. THE indisposition of my health, which drove me out of London, and keeps me still in the country, must be an excuse for my so long silence. The very great civility you express to me in your letter makes me hope your pardon for the slowness of my answer, whereby I hope you will not measure the esteem and respect I have for you. That your own distinguishing merit, amongst the rest of my countrymen I met with at Leyden, has so settled in me, that before the occasion your brother's favour lately gave me to inquire after you, I often remembered you, and it was not without regret I considered you at a distance that allowed me not the hopes of renewing and improving my acquaintance with you. There being nothing I value so much as ingenious knowing men, think it not strange that I laid hold on the first opportunity to bring myself again into your thoughts. You must take it as an exercise of your goodness, drawn on you by your own merit; for, whatever satisfaction I gain to myself in having recovered you again, I can propose no advantage to you, in the offer of a very useless and infirm acquaintance, who can only boast that he very much esteems you.

That which I always thought of Dr. Sydenham living, I find the world allows him now he is dead, and that he deserved all that you say of him. I hope the age has

many who will follow his example, and by the way of accurate practical observation, as he has so happily begun, enlarge the history of diseases, and improve the art of physic, and not by speculative hypotheses fill the world with useless, though pleasing visions. Something of this kind permit me to promise myself one day from your judicious pen. I know nothing that has so great an encouragement from mankind as this.

I beg you to present my most humble service to your brother, whom I forbear now to interrupt, in the midst of his parliamentary affairs, whereof I know a great part must fall to his share, with my thanks for the favour of his of the 15th of October, which lately found me out safe here. Let him know that I am exceedingly sensible of the obligation, and shall at large make my acknowledgments to him as soon as good manners will allow it. I am,

I AM much concerned to hear you have your health no better, and on this occasion cannot but deplore the great losses the intellectual world in all ages has suffered, by the strongest and soundest minds possessing the most infirm and sickly bodies. Certainly there must be some very powerful cause for this in nature, or else we could not have so many instances where the knife cuts the sheath, as the French materially express it: and if so, this must be reckoned among the many other inseparable miseries that attend human affairs.

I could wish the physician's art were so powerful and perfect, as, in some measure, to prevent so great an evil; but we find where once nature, or the "Economia Animalis" of the body, is so depraved as not to cooperate with medicine, all remedies, and the courses of them, prove wholly ineffectual, or to very little purpose. But still the more imperfect physic is, so much the more is owing to those who in the least improve so difficult a province, which certainly has been considerably advanced by some late English authors; and that puts me in mind to desire of you your thoughts, or what other learned physicians you converse with say, concerning Dr. Morton and his late Exercitations on Fevers. As for his general theory of them, I esteem it, as all others of this kind, a sort of mere waking dream, that men are strangely apt to fall into, when they think long of a subject, beginning quite at the wrong end; for by framing such conceits in their fancies, they vainly think to give their understandings light, whilst the things themselves are still, and perhaps ever must remain, in darkness.

In his first exercitation that treats of agues, I do not find he has said any thing very material, or worth notice, that the world did not sufficiently know before, unless it were some histories of the irregular shapes and symptoms this distemper appears under, which I think may be very instructive to the physician, and of great ease and advantage to the sick.

But his practical remarks in his second exercitation about continuing and remitting fevers, if they be judiciously founded upon many and steady observations, so that they may safely pass into a rule, must certainly be of great moment in directing the management and cure of fevers. I confess my experience in this distemper as yet falls something too short for to determine positively, whether all his observations be real and well grounded; but, as far as I can judge at present, several of them do hold good.

I remember to have heard Dr. Morton was once a presbyterian preacher; and though he were, this does not make him a jot the less capable, in above twenty

years' practice, to have carefully observed the accidents that naturally occur in the progress of a disease; and if he be but a true and judicious register, it is all I desire from him.

You see I have taken great freedom in giving a character according to my apprehensions of this author, but it is only to encourage you to use the same liberty; for if, at your leisure, you would let me know your own thoughts, or what other candid men say concerning him and his methods of cure, or any other useful tract that comes abroad, you will extremely oblige,

Sir,

Your most obedient humble servant,

THO. MOLYNEUX.

Mr. Locke to Dr. Molyneux.

Oates, Jan. 20, 169.

SIR, I MUST acknowledge the care you take of my health, in a way wherein you so kindly apply to my mind; and if I could persuade myself that my weak constitution was owing to that strength of mind you ascribe to me, or accompanied with it, I should find therein, if not a remedy, yet a great relief against the infirmities of my body. However, I am not the less obliged to you for so friendly an application; and if the cordial you prescribe be not to be had (for I know none equal to a judicious and capacious mind) your kindness is not to be blamed, who I am confident wish me that satisfaction, or any thing else that could contribute to my health.

The doctor, concerning whom you inquire of me, had, I remember, when I lived in town, and conversed among the physicians there, a good reputation amongst those of his own faculty. I can say nothing of his late book of fevers, having not read it myself, nor heard it

spoke of by others: but I perfectly agree with your concerning general theories, that they are, for the most part, but a sort of waking dreams, with which, when men have warmed their own heads, they pass into unquestionable truths, and then the ignorant world must be set right by them: though this be, as you rightly observe, beginning at the wrong end, when men lay the foundation in their own fancies, and then endeavour to suit the phenomena of diseases, and the cure of them, to those fancies. I wonder that, after the pattern Dr. Sydenham has set them of a better way, men should return again to that romance way of physic. But I see it is easier, and more natural, for men to build castles in the air, of their own, than to survey well those that are to be found standing. Nicely to observe the history of diseases in all their changes and circumstances, is a work of time, accurateness, attention, and judgment, and wherein if men, through prepossession or oscitancy, mistake, they may be convinced of their error by unerring nature and matter of fact, which leaves less room for the subtlety and dispute of words, which serves very much instead of knowledge, in the learned world, where, methinks, wit and invention has much the preference to truth. Upon such grounds as are the established history of diseases, hypotheses might with less danger be erected, which I think are so far useful, as they serve as an art of memory to direct the physician in particular cases, but not to be relied on as foundations of reasoning, or verities to be contended for; they being, I think I may say all of them, suppositions taken up gratis, and will so remain, till we can discover how the natural functions of the body are performed, and by what alteration of the humours, or defects in the parts, they are hindered or disordered. To which purpose, I fear the Galenists' four humours, or the chemists' sal, sulphur, and mercury, or the late prevailing invention of acid and alkali, or whatever hereafter shall be substituted to these with new applause, will, upon examination, be found to be but so many learned empty sounds, with no precise determinate signification. What we know of the works of nature, especially in the constitution of health, and the