Principles of Morals," which is one of the clearest expositions of the leading principles of what is termed the utilitarian system. Hume died on August 25, 1776. _I.--Doubts Concerning the Understanding_ All the objects of human reason or inquiry may naturally be divided into two kinds--to wit, _relations of ideas_ and _matters of fact_. Of the first kind are the sciences of geometry, algebra, and arithmetic, and, in short, every affirmation which is either intuitively or demonstratively certain. "That the square of the hypotenuse is equal to the squares of the two sides" is a proposition which expresses a relation between these figures. "That three times five is equal to the half of thirty" expresses a relation between these numbers. Propositions of this kind are discoverable by the mere operation of thought, without dependence on what is anywhere existent in the universe. Though there never were a circle or triangle in nature, the truths demonstrated by Euclid would for ever retain their certainty and evidence. Matters of fact, which are the second objects of human reason, are not ascertained in the same manner; nor is our evidence of their truth, however great, of a like nature with the foregoing. The contrary of every matter of fact is still possible, because it can never imply a contradiction, and is conceived by the mind with the same facility and distinctness as if ever so conformable to reality. "That the sun will not rise to-morrow" is no less intelligible a proposition, and implies no more contradiction, than the affirmative that "it will rise." We should in vain, therefore, attempt to demonstrate its falsehood. Were it demonstratively false, it would imply a contradiction, and could never be distinctly conceived by the mind. It may, therefore, be a subject worthy of curiosity to inquire what is the nature of that evidence which assures us of any real existence of matters of fact beyond the present testimony of our senses, or the records of our memory. All reasonings concerning matter of fact seem to be founded on the relation of _cause_ and _effect_. If we would satisfy ourselves, therefore, concerning the nature of that evidence which assures us of matters of fact, we must inquire how we arrive at the knowledge of cause and effect. I shall venture to affirm, as a general proposition which admits of no exception, that the knowledge of this relation is not, in any instance, attained by reasonings _a priori_, but arises entirely from experience.