Tom, you are correct that we see further as we go higher up.
...on a Round Earth, that's because being higher allows you to see past the curvature of the Earth. In Flat Earth, that's not the case. You should be able to see exactly the same distance no matter how high you are - because (we're told) the clarity of the atmosphere is the limiting factor. If that were true then if you're looking at things on the ground, you'd actually be able to see LESS far as you gain in height.
But what i think is being questioned is why or how can we see the sun if it's already past a vanishing point?
Except that this "vanishing point" thing (along with "perspective") is just confusing the poor FE'ers. Talking about how light is projected onto the back of the eye (or a pinhole camera) makes for a MUCH simpler argument. The thing is that Tom doesn't want a much simpler argument - he needs something that he hopes will confuse people sufficiently to throw them off the scent.
Think of an aircraft flying away from you. It gets smaller and smaller as it moves further away. An increase in viewing height would not bring it back into view.
In FET, that should be true - but weird-perspective can do anything Tom decrees it should do...so all bets are off.
So if the sun, according to the FE model, is 'flying' away from us like an aircraft then how can we bring it back into view by increasing our height?
Also, why doesn't the sun get smaller in size as its 'flying' away form you?
Exactly. And Tom's altered perspective has a SERIOUS problem. If it worked equally in all directions - then the effect should scrunch things off to the sides of your field of view into the center - resulting in a weird curvature of things like long straight train tracks. If it only works in the vertical direction and it's an optical effect inside your eye/brain - then viewing the sun while laying on your side would allow you to see the sun high in the sky at "sunset". If it only works in the vertical direction (as in perpendicular to the flat plane of the Earth) - then the sun would become more and more elliptical as it approached the horizon - and distant trees and buldings would appear to be flattened.
Since NONE of these three things happen - we know that Tom's argument is nonsense.
But since he refuses to elaborate beyond posting a diagram with a bunch of lines going ever which way from a 150 year old book (which itself does nothing to elaborate on the issues with the concept) - we're left with nothing to go on.
Hence, let's just go back to first principles and ask how the sun forms an image onto the back of a simple pinhole camera. That is the simplest possible optical system that exhibits perspective - and from it we can deduce a mathematical statement of how perspective operates - and thereby demonstrate beyond doubt that the sun doesn't set on the round earth.
Which puts Tom back with the antiquated FE claim that electromagnetic acceleration explains the sunset by allowing light rays to curve...which then produces the same set of problems that I outlined above. If electromagnetic acceleration was the cause of sunsets - then the sun would be circular only when directly overhead - and would become increasingly elliptical as it moved toward the horizon. Ditto for the moon. Worse still, it would compress the star field towards the horizon and there would be a LOT more stars at the horizon than overhead at any given time of the day or night.
You can push this flat earth horseshit only just so far - and then it breaks. That's because it's not true! Truth will out!