Great question! So when I mentioned “womanhood [as] some discrete form that exist[s] in the world like a mineral composition,” I think there’s a reasonable chance that Walsh is searching for, essentially, the Platonic Form of “woman” — disregarding the content of the actual in search of the ideal.
The unfortunate consequence of Platonic Forms is that they tend to lead to an infinite regress when they’re scrutinized through this process. In order to define the Form of “woman” we necessarily need to define “human” which then entails defining “life” — and how can I hope to do that without defining “reality” first? To further complicate things, if all elements of reality have their own Form that governs them definitionally and if Forms actually exist, then there would also be a Form that governs Form. And on and on. You can see where this ends up.
Within the film’s internal narrative of Walsh seeking to figure out his daughter, if he needs to learn the truth about her before he can then understand her, I think he’s missing the point. We don’t dissect and catalog people before we can understand them, we engage with them in genuine, meaningful experiences to understand them. Further, while truth suggests a discrete — potentially even static — reality, understanding is a continuous and ongoing process of engagement and reassessment.