420 INTRODUCTORY LECTURES. 



any modern labours upon the same plan are of very little value: 

 It is therefore the dogmatic systems to which we are chiefly 

 obliged for the facts we have already acquired ; but it is not 

 quite so obvious that the same study must still conduct us in 

 our farther collection ; I shall however endeavour to prove it in 

 this manner. 



In the course of my history, in giving an account of the Em- 

 piric sect, I took occasion to explain the nature of their plan, 

 and told you that it consisted of three parts, Observation, History, 

 and Analogy ; and I can now say that if this plan could be as 

 easily executed, and as successfully applied as the Empirics 

 supposed, we should have few objections to its being the 

 sole plan in physic. But it is more specious than practicable. 

 Observation is extremely difficult : it requires the knowledge of 

 a number of circumstances that are not always obvious, that are 

 very often hidden in their nature, or concealed of design. Even 

 with regard to the more obvious circumstances, observations re- 

 quire an attention to such a variety and series of facts, as few men 

 are equal to ; and, from both considerations, they are so difficult 

 to make, that but few good or complete observations have at any 

 time bgen collected. It is plain that they can be rendered 

 complete only by opportunities of being frequently repeated. If 

 we consider this, with the prodigious number of subjects upon 

 which observation is required, we shall readily perceive that the 

 work of one man's life can go but a little way in this business ; 

 and the empirics properly enough perceived, that the stock of 

 facts necessary to their plan must be the work of ages, accumu- 

 lated in History. But this does not relieve their plan of its 

 difficulties ; for history must partake of all the imperfections and 

 inaccuracies of observation, and might continue these faults by 

 seeming to supersede the repetition which was necessary to cor- 

 rect them. But further, when we consider that the particulars 

 of observation are often sensations difficult to be communicated ; 

 that they are often estimates made by our senses, very different 

 in different persons ; that all these, as conveyed in history, are 

 under the imperfections of language and men's different inter- 

 pretations of this ; we shall perceive that history not only carries 

 on the inaccuracy of observation, but also greatly increases its 

 imperfection. If to all this we add what we are well assured of, 



