Shonin wrote:What does Theravada say about "the illusion of all phenomenal existence" ?
One thing that is clearly said is the all dhammas are empty of any sort of self existing thingness.
Well, that's what I thought. And this is what Mahayana teaches too. Ideas about it being illusion are not universally regarded as useful in Mahayana.
I recall debating with at least one Theravadin who insisted that Anatta did not mean "all dhammas are empty of any sort of self existing thingness" (and thus that it meant the same as Sunyata as I was arguing) and that rather it only implied that 'I' don't have self-existing thingness, that no phenomena are me, mine etc. Yet it seems hard to see the notion that I don't have self-existing thingness, while my dog and the carrot in the fridge do, as a coherent philosophy.