David Hume 
Enquiries Concerning the Human Understanding [PDF ebook] 
And Concerning the Principles of Morals

Whilst the greatest effort has been made to ensure the quality of this text, due to the historical nature of this content, in some rare cases there may be minor issues with legibility. Were the generality of mankind contented to prefer the easy philosophy to the abstract and profound, without throw ing any blame or contempt on the latter, it might not be improper, perhaps, to comply with this general Opinion, and allow every man to enjoy, without Opposition, his own taste and sentiment. But as the matter is often carried farther, even to the absolute rejecting of all profound reasonings, or what is commonly called metaphysics, we shall now proceed to consider what can reasonably be pleaded in their behalf.