A much-belated side-note for anyone who happens to come by:

Interestingly, the words 'empathy' and 'sympathy' have not been used consistently across different academic disciplines. (This has little direct significance to Aaronson's post; I am merely remarking on a use of language that may indirectly cause confusion.) I was doing a quick review of the psychopathy literature, and found that the word 'sympathy' is not used at all – it seems to be described instead by 'affective empathy'.

Batson (2009) wrote in detail about this in The Social Neuroscience of Empathy (bold emphasis mine):

Among philosophers, coming to feel as the other feels has often been called “sympathy,” not empathy (Hume, 1740/1896; Smith, 1759/1853). Among psychologists, it has been called “emotional contagion” (Hatfield, Cacioppo, & Rapson, 1994), “affective empathy” (Zahn-Waxler, Robinson, & Emde, 1992), and “automatic emotional empathy” (Hodges & Wegner, 1997).

[...]

Other-oriented emotion felt when another is perceived to be in need has not always been called empathy. It has also been called “pity” or “compassion” (Hume, 1740/1896; Smith, 1759/1853), “sympathetic distress” (Hoffman, 1981, 2000), and simply “sympathy” (Darwall, 1998; Eisenberg & Strayer, 1987; Preston & de Waal, 2002; Sober & Wilson, 1998; Wispé, 1986).

[...]

It would simplify matters if empathy referred to a single object and if everyone agreed on what that object was. Unfortunately, as with many psychological terms, this is not the case. Both empathy and sympathy (the term with which empathy is most often contrasted) have been used in a variety of ways. Indeed, with remarkable consistency exactly the same state that some scholars have labeled empathy others have labeled sympathy. I have discerned no clear basis—either historical or logical—for favoring one labeling scheme over another. The best one can do is recognize the different phenomena, make clear the labeling scheme one is adopting, and use that scheme consistently.