We may here take occasion to mention a principle, distinct from all the internal senses, from which taste will, in many instances, receive assistance. It is such a sensibility of heart, as fits a man for being easily moved and for readily catching, as by infection, any passion that a work is fitted to excite. The souls of men are far from being alike susceptible to impressions of this kind. A hard-hearted man can be a spectator of very great distress, without feeling any emotion: A man of a cruel temper has a malignant joy in producing misery. On the other hand, many are composed of so delicate materials, that the smallest uneasiness of their fellow-creatures excites their pity.
Here, Gerard speaks of the "heart" as though it operated after the manner of an (internal or external) sense organ. Thus, different people have hearts that are more or less sensitive. Interestingly, Gerard also indicates the possibility that the heart can be perverse. That is, in a "man of a cruel temper" the perception of pain in others may actually give rise to pleasure.