In writing about the poet Basho, Harold Henderson in his book An Introduction to Haiku writes "It is...worthy to note that whenever Basho uses the word "dream" he seems also to be thinking of human life; and perhaps it is even more noteworthy that to him the "illusion" of the world does not seem to mean that it is in any sense unreal, but rather, as with St.Thomas Aquinas,that it is far more real than it seems".I'm not sure the Aquinas comparison holds. Or rather maybe it holds in the negation only.
What we call reality is an illusion made with our senses and mind. That in no way denies the reality of the manifest world. It merely means we are dreaming a consensual human reality.
Where Aquinas would hold that it’s the soul and afterlife that is true reality, I believe Basho would hold to a more nondual vision that all is actually God, or Spirit.
Aquinas would see the world as a testing or proving ground to attain the beauty of heaven. For Basho, the world was instead the essence of beauty itself.
The illusion is seeing it as anything but.