The book which argues (among other things) that the foundations of morals lie with sentiment, not reason has been translated into Persian by Morteza Mardiaha. Tehran-based Parseh Publishing has released 'An Enquiry Concerning the Principles of Morals' in 228 pages.

The work is the enquiry subsequent to the Enquiry Concerning Human Understanding (EHU). Thus, it is often referred to as "the second Enquiry". It was originally published in 1751, three years after the first Enquiry.

Hume first discusses ethics in 'A Treatise of Human Nature' (in Book 3 - "Of Morals"). He later extracted and expounded upon the ideas he proposed there in his second Enquiry. In his short autobiographical work, 'My Own Life' (1776), Hume states that his second Enquiry is "of all my writings, historical, philosophical, or literary, incomparably the best."

Here, Hume defends his sympathy-based moral sentimentalism by claiming that, contrary to moral rationalism, we can never make moral judgments based on reason alone. Reason deals with facts and draws conclusions from them, but, all else being equal, it could not lead us to choose one option over the other; only our sentiments can do this, according to Hume. Hume writes that:

"…morality is determined by sentiment. It defines virtue to be whatever mental action or quality gives to a spectator the pleasing sentiment of approbation; and vice the contrary."

According to Hume, our sympathy-based sentiments can motivate us towards the pursuit of non-selfish ends. For Hume, and for fellow sympathy-theorist Adam Smith, the term "sympathy" is meant to capture much more than concern for the suffering of others.

Sympathy, for Hume, is a principle for the communication and sharing of sentiments, both positive and negative. In this sense, it is akin to what contemporary psychologists and philosophers call empathy.

In developing this sympathy-based moral sentimentalism, Hume surpasses the divinely-implanted moral sense theory of his predecessor, Francis Hutcheson, by elaborating a naturalistic, moral psychological basis for the moral sense, in terms of the operation of sympathy.

After providing various examples, Hume comes to the conclusion that most, though not all, of the behaviors we approve of increase public utility. Does this then mean that we make moral judgments on self-interest alone? Unlike his fellow empiricist Thomas Hobbes, Hume argues that this is not in fact the case, rejecting psychological egoism—the view that all intentional actions are ultimately self-interested.