What result will follow upon the collision, in the impelling ball? Will it continue to move in the same direction? Will it recoil in the opposite direction? Will it fly off obliquely; or will it subside into a state of rest? All these events will be found equally probable by him whom a series of observations upon the past has not instructed as to what he is to expect from the future.
From these remarks we may sufficiently collect what is the species of knowledge we possess respecting the laws of the material universe. No experiments we are able to make, no reasonings we are able to deduce, can ever instruct us in the principle of causation, or show us for what reason it is that one event has, in every instance in which it has been known to occur, been the precursor of another event of a given description. Yet this observation does not, in the slightest degree, invalidate our inference from one event to another, or affect the operations of moral prudence and expectation.
The nature of the human mind is such as to oblige us, after having seen two events perpetually conjoined, to pass, as soon as one of them occurs, to the recollection of the other: and, in cases where this transition never misleads us, but the ideal succession is always found to be an exact copy of the future event, it is impossible that this species of foresight should not be converted into a general foundation of inference and reasoning.
We cannot take a single step upon this subject which does not partake of the species of operation we denominate abstraction. Till we have been led to consider the rising of the sun tomorrow as an incident of the same species as its rising today, we cannot deduce from it similar consequences. It is the business of science to carry this talk of generalization to its furthest extent, and to reduce the diversified events of the universe to a small number of original principles.