Of all the terms that we employ in treating of human affairs, those of _natural_ and _unnatural_ are the least determinate in their meaning. Opposed to affectation, frowardness, or any other defect of the temper or character, the natural is an epithet of praise; but employed to specify a conduct which proceeds from the nature of man, can serve to distinguish nothing; for all the actions of men are equally the result of their nature. At most, this language can only refer to the general and prevailing sense or practice of mankind; and the purpose of every important enquiry on this subject may be served by the use of a language equally familiar and more precise. What is just, or unjust? What is happy or wretched, in the manners of men? What, in their various situations, is favourable or adverse to their amiable qualities? are questions to which we may expect a satisfactory answer; and whatever may have been the original state of our species, it is of more importance to know the condition to which we ourselves should aspire, than that which our ancestors may be supposed to have left. SECTION II. OF THE PRINCIPLES OF SELF PRESERVATION. If in human nature there are qualities by which it is distinguished from every other part of the animal creation, this nature itself is in different climates and in different ages greatly diversified. The varieties merit our attention, and the course of every stream into which this mighty current divides, deserves to be followed to its source. It appears necessary, however, that we attend to the universal qualities of our nature, before we regard its varieties, or attempt to explain differences consisting in the unequal possession or application of dispositions and powers that are in some measure common to all mankind.