And Jesus said unto them, 'Who do you say that I am?'
And they replied, 'You are the eschatological manifestation of the ground of our being, the kerygma in which we find the ultimate meaning of our interpersonal relationships.'
And Jesus said: 'What?'
We've moved away from trying to define things in terms of essence, and tried to define things operationally instead. Ask a scientist what's an electron, and you'll get what boils down to "something that acts like thus and so, with a negative charge, mass of 511KeV/c^2, etc." If it looks like a duck, walks like a duck, and quacks like a duck, its a duck.
Studying operations has been very fruitful in mathematics; ditto mappings. Turning from "what is it" to "what does it do" is what much of science is about. i.e. "Shut up and compute." That's helpful in designing systems, and it helps avoid arguments about a whether will is associated with a person or a nature.
Seriously--when you talk about Jesus' nature as human and divine, you have to remember that "nature" doesn't have quite the same meaning when referring to the Origin of all nature. I suppose I should spend a little time researching whether Divine Simplicity shows up in Christological analysis. The first pages didn't turn anything up, but google is hardly ideal for that sort of research.
And yet... We easily take "operationalism" too far. Twins may look and act alike, but they are different people. There's an essence-ial difference.
I don't know where it is proved that we can only know things by comparison with other things. The claim that all knowledge comes through the senses presumes that there is no intrinsic knowledge, it doesn't prove it. I think there is such a thing. So long as we are careful to understand the limits of our words (another thing philosophers love to squabble over) we should be able to say true things about essentials, and not just interactions.
You'd think this would be a more popular notion, given the current "trans" fashion that claims that their essence doesn't match their bodies, and that a little cargo-cult magic will make everything right.