Haecceitist

Probably, most of us are Haecceitists with respect to most things through time, but the very inaccessibility of other possible worlds seems to have produced a goodly number of Anti-Haecceitists with respect to trans-world identifications. Even when their quantified modal logics look Haecceitistic, their pre-systematic remarks may explain the so-called identities as a manner of speaking.

Source: wiktionary

Here we find the dividing line between Haecceitism and anti-Haecceitism. The Haecceitist holds that members of each pair differ from each other. The anti-Haecceitist denies this. This has a consequence for Combinatorialism. The anti-Haecceitist Combinatorialist will countenance fewer possible worlds than the Haecceitist does.

Source: wiktionary

But a naive haecceitist would assert that when he perceives an external object he has a self-evident intuition that he grasps the haecceity of that object. Presumably, if a naive haecceitist grasps a haecceity of an external object in this way, then he can know that he grasps this haecceity.

Source: wiktionary

[…] I argued that all we have here are just two verbally different formulations to which no ontological distinction corresponds. I called this position anti-haecceitist. A haecceitist was thus defined as one who holds that the two worlds are genuinely different.

Source: wiktionary