CHAP. XXII.] CONSTITUTION OF THE INTELLECT. 403 



That to such questions as the above, no single and general 

 answer can be given, must be evident. There are cases in which 

 they do not even need discussion. Instances are familiar, in 

 which general propositions merely express per enumerationem 

 simplicem, a fact established by actual observation in all the 

 cases to which the proposition applies. The astronomer as- 

 serts upon this ground, that all the known planets move from 

 west to east round the sun. But there are also cases in which 

 general propositions are assumed from observation of their truth 

 in particular instances, and extension of that truth to instances 

 unobserved. No principle of merely deductive reasoning can 

 warrant such a procedure. When from a large number of ob- 

 servations on the planet Mars, Kepler inferred that it revolved 

 in an ellipse, the conclusion was larger than his premises, or in- 

 deed than any premises which mere observation could give. 

 What other element, then, is necessary to give even a prospective 

 validity to such generalizations as this ? It is the ability in- 

 herent in our nature to appreciate Order, and the concurrent pre- 

 sumption, however founded, that the phenomena of Nature are 

 connected by a principle of Order. Without these, the general 

 truths of physical science could never have been ascertained. 

 Grant that the procedure thus established can only conduct us 

 to probable or to approximate results ; it only follows, that the 

 larger number of the generalizations of physical science possess 

 but a probable or approximate truth. The security of the tenure 

 of knowledge consists in this, that wheresoever such conclusions 

 do truly represent the constitution of Nature, our confidence in 

 their truth receives indefinite confirmation, and soon becomes 

 undistinguishable from certainty. The existence of that prin- 

 ciple above represented as the basis of inductive reasoning 

 enables us to solve the much disputed question as to the neces- 

 sity of general propositions in reasoning. The logician affirms, 

 that it is impossible to deduce any conclusion from particular 

 premises. Modern writers of high repute have contended, that 

 all reasoning is from particular to particular truths.. They in- 

 stance, that in concluding from the possession of a property by 

 certain members of a class, its possession by some other member, 

 it is not necessary to establish the intermediate general conclu- 



2D2 



