But, in the _second_ place, should it be asked, whether we ought to search for these principles in _nature_, or whether we must look for them in some other origin? I would reply, that our answer to this question depends upon the definition of the word Nature, than which there is none more ambiguous and equivocal. If _nature_ be opposed to miracles, not only the distinction betwixt vice and virtue is natural, but also every event which has ever happened in the world, _excepting those miracles on which our religion is founded_. In saying, then, that the sentiments of vice and virtue are natural in this sense, we make no very extraordinary discovery. But _nature_ may also be opposed to rare and unusual; and in this sense of the word, which is the common one, there may often arise disputes concerning what is natural or unnatural; and one may in general affirm, that we are not possessed of any very precise standard by which these disputes can be decided. Frequent and rare depend upon the number of examples we have observed; and as this number may gradually increase or diminish, 'twill be impossible to fix any exact boundaries betwixt them. We may only affirm on this head, that if ever there was any thing which could be called natural in this sense, the sentiments of morality certainly may; since there never was any nation of the world, nor any single person in any nation, who was utterly deprived of them, and who never, in any instance, showed the least approbation or dislike of manners. These sentiments are so rooted in our constitution and temper, that, without entirely confounding the human mind by disease or madness, 'tis impossible to extirpate and destroy them. But _nature_ may also be opposed to artifice, as well as to what is rare and unusual; and in this sense it may be disputed, whether the notions of virtue be natural or not. We readily forget, that the designs and projects and views of men are principles as necessary in their operation as heat and cold, moist and dry; but, taking them to be free and entirely our own, 'tis usual for us to set them in opposition to the other principles of nature. Should it therefore be demanded, whether the sense of virtue be natural or artificial, I am of opinion that 'tis impossible for me at present to give any precise answer to this question. Perhaps it will appear afterwards that our sense of some virtues is artificial, and that of others natural. The discussion of this question will be more proper, when we enter upon an exact detail of each particular vice and virtue.[4]