We will eventually come up against something that cannot be varied without destroying that object as an instance of its kind. The implicit claim here is that if it is inconceivable that an object of kind K might lack feature F, then F is a part of the essence of K.
It seems that I cannot vary existence out of the transcendental ego. However hard I try to erase every part from it, the transcendental ego includes at least one percept; it exists. That suggests its essence is existence, which Aquinas uses to describe God or the first cause.
I think I can do so with other things. Maybe the skin of this apple is an illusion, the red apple is in fact green, so the apple is not essentially red and its redness does not essentially exist.
Reality can be compared to the wood. Imagination is like the perception of the elephant. Duality can be seen as the elephant.
https://info-buddhism.com/Vasubandhu-Three_Natures-Garfield.html
If it necessarily exists and we cannot imagine it is a hallucination, is the transcendental ego the dependent reality that we should realise appears as, but is not, a hallucination (the piece of wood we mistake as an elephant)?
I'm really confused by this.
It may help to know what Husserl thought existence to the transcendental ego meant.