Essay on the Nature and Conduct of the Passions (1728)

yet it is difficult to explain. This difficulty probably arises from our previous notions of a small number of senses, so that we are unwilling to resort in our theories to any more; we would rather strain to find some explanation of moral ideas in relation to some other natural powers of perception that are universally acknowledged. A similar difficulty attends several other perceptions, to which philosophers have not generally assigned their own distinct senses; such as natural beauty, harmony, the perfection of poetry, architecture, design, and similar matters of genius, taste, or fancy: The explanations or theories on these subjects are likewise full of confusion and metaphor.

To define virtue by its agreeableness to this moral sense, or to describe it as kind affection, may