m 
Introduction . 9 
of Dcmonílration . That which I have taken here indeed is neither fo ítriétly demonitrative as maticians require in all its Steps , or fo concife as might be - , becaufe I have contrived it only in fuch a Manner as to prove to a Pcrfon that never before heard of it , that the Proportion is certainly true , and to illuftrate that particular Procedure , which the Mind neceiTarily takes in all its Enquiries of the like Nature . 
Thus far I believe is attended with no Manner of Difficulty , although perhaps fomc are by this Time ready to afk , What has all this to do with Phyfick ? My Bufinefs therefore next fhall be to ihew , that all our Knowledge of the Operations and Effects of phyfical Agents , that is , of all the Alterations and Changes that are brought about in the vifible World by the immediate Agency of phyfical Caufes - , to íhew , I fay , that all our Knowledge of thefe ters is taken in by the fame Means , and depends together upon the fame Evidences . After which I fliall endeavour to apply it to Medicine , and prove , that all we can know of a Human Body , both with Regard to the Frame and Mechanifm of its Parts , and to the rectifying of its Diforders , to be likewifc upon the fame Principles . 
The firft of thefe 1 expert will be anfwercd , when it appears that all the eflential Properties of Matter ( fuch Properties I mean , as are infeparable from it under what particular Mode or Form foever it exifts ) are no other than what our Senfes very clearly and diftinétly difcover to us , and that we have no other Way of knowing them but by their Information . And to this Purpofe it will be very convenient to go over the firfl : Notices we have herein by thefe Afliftan - ccs ; that is , thofe Properties of Matter or Body , which from the Tcftimony of our Senfes are demon - ítrative and felt - evident , and which cannot but cite