[1] Some prominent figures in the history of philosophy who have defended moral rationalism are Plato and Immanuel Kant.
Recent philosophers who have defended moral rationalism include Richard Hare, Christine Korsgaard, Alan Gewirth, and Michael Smith.
Moral rationalism is similar to the rationalist version of ethical intuitionism; however, they are distinct views.
In Book 3 of A Treatise of Human Nature and in An Enquiry Concerning the Principles of Morals (EPM), Hume argues (among other things) that reason and emotions (or the "passions" as he often calls them) are quite distinct faculties and that the foundations of morality lie in sentiment, not reason.
It defines virtue to be whatever mental action or quality gives to a spectator the pleasing sentiment of approbation; and vice the contrary" (EPM, Appendix 1, ¶10).