It seems like many of the Entities have a visceral/instinctive component and a linked existential/philosophical (?) component. Some seem pretty intuitive: the Vast, for instance. Agoraphobia/acrophobia for the instinctive, fear of humanity's personal and cosmic insignificance for the existential. But others seem more arbitrary: fear of fire/fear of loss or destruction are plausibly linked, sure, but fear of spiders doesn't seem to have much to do with fear of manipulation, at least for me. And of course there are several that don't fit this rubric: the Lonely and the End are almost purely existential, the Filth purely visceral. Idk, Gerard Keay would probably say I'm quibbling over whether indigo's a separate color or just counts as dark blue.