Which we had, in our thematical solution, assessed as a phenotypic essential part, implying that it does not, as a genuine replaceable determination does (involving partly overlap), inhere in a subject, except in cases where the causal path leading from the genotypic essential part (cause) to the corresponding phenotypic essential part (effect) is very long, allowing the latter to be replaced by another determination while the genotypic make-up remains the same, as we see it in the case of CAPABLE OF LAUGING with respect to man (considered as a species). And the present discussion, dealing with how St Thomas is trying to distinguish between proprium, accidens, and essence, involves just such propria, that is determinations, although in a way, per se, are nevertheless more or less like replaceable determinations, and are thus considered, not to be (wholly) a part of the substrate (subject), but (partly) lying outside it like genuine replaceable determinations do. So while, say, Space Group P63 2 / m 2 / c is a phenotypic essential part of an Ice crystal, and thus a specific or generic proprium, and moreover, a determination that lies totally inside the substrate (see the above depicted diagram ), CAPABLE OF LAUGHING is also phenotypic and, because it is specific, should also be considered as lying totally inside the substrate, but, because of the reasons mentioned, nevertheless lies, in a way, outside the substrate. And as such it is considered by St Thomas.