18 



13. A tree: why does it exist? upon what does its existence 

 depend? or, why is it a tree? It is made such by its roots, trunk, 

 and branches; without these it would be no tree: these are the 

 parts of a tree ; and if these parts are necessary to the definition of 

 a tree (which may be arbitrary, and is of no consequence), to the 

 identity of a tree, why then the tree could not exist without them. 

 But then these parts what makes them? The aggregation and 

 arrangement of ligneous fibres. What determines this aggregation 

 and arrangement of fibres? Certainly some cause; for the fibres, 

 if not endowed with this property, or if not affected by some agent, 

 would never aggregate or become arranged. We come at last to 

 examine the origin of the fibres: what makes them? Their par- 

 ticles of the same nature make their bulk; and other constituents, 

 which chymistry to some extent can display, make their nature. 

 Then these particles how are they made? Shall we say by par- 

 ticles still more minute, and by chymical properties? Thus far we 

 may go with the witness of the senses, at last we shall arrive at what 

 are termed elements; and if these elements can exist without the 

 condition of existence before expressed, viz. that they also must be 

 produced by some cause, why then we must give up the universality 

 of our axiom. 



14. As far as our experience goes of the origin of things (and 

 we have an ample experience in this way, no less than that which 

 comprises all our knowledge of processes or of occurrences), we do 

 not know a single example in which the condition of existence is 

 not this, viz. that the thing would not exist, but for a process of 

 formation, or unless it were made by appropriate causes. The 

 elementary substances and particles, it will be said, are exceptions; 

 what then, do we know that these are truly elements^ mere units, 

 comprising in their existence only a single property ? No, it must 

 be replied, we do not know this; but here our analyses end. This 

 then is the state of the argument : nine tenths of the objects of 

 which we have any cognizance, are made perceptibly by causes; 

 that is, all the objects, the terms of whose existence we are ac- 

 quainted with, acknowledge this necessity of a causation, without 

 which they would not exist (and where shall we apply for a know- 

 ledge of these terms, but where they are manifested to the sensesT). 

 There are other objects whose origins we know nothing about, and 

 by which, consequently, we are furnished with no experience (and 

 therefore with no grounds for a conclusion); objects, of whose con- 

 ditions of existence we are not qualified for a sensible testimony ; 

 and the inference is, that these latter require the same process of 

 causation as the former. 



15. The strength of the inference is this : from things seen (or 

 witnessed by a sense) we infer things not seen; we do this as 

 before explained, upon the ground of analogy. In the present 

 instance, is the analogy perfect ? It is unexceptionably perfect : for 

 what are the terms of existence? is the question; and it will not be 

 denied that the existence is mutual, that it obtains throughout, and 



