Another perspective on this "illusion" is historical as from remote times mankind has had an atavistic consciousness which displays a penetration of the human being within the external world. In the ancient Egyptian, or chaldanean, or ancient Indian consciousness it was seen that the external world was the sense bound perception of a spirituality.
There was no doubt of the existence of the spiritual world for each man was immersed , to a greater or lesser extent, within that world. When the shepherd laid down a night the images of the stars appeared to him and he knew these images, or specifically beings, were real and the underpinning of the sense bound realities were these very beings.
This was the world of the gods of the hearth, or the fields or "little people" etc..to which names were given to these beings whose outward projection was our sense bound impressions. To the ancient man, all to which he was immersed was the outward projection of the Divine . the sun was perceived as the sense bound manifestation of the Sun God Ra or Ahura Mazda with names appropriately given through a revelatory consciousness.
And so, the Ancient Indian had a term for these sense bound impressions called "Maya" or the "great illusion" . I suspect that the modern philosophers referenced in this thread, having no consideration for the Divine, perforce placed this "illusion" within man himself, an error of the most inappropriate logic, the logical failure.
Its true that what we see is an "illusion" or "Maya" for the reality is that very spiritual world to which our senses do not manifest. Up to the 15th century of our era there was a marginal appreciation of this spiritual world so that there was no doubt of divinity manifesting within and without the human soul.
We, since the intellect has gained strength within each man (15th century), have no appreciation of the Divine but we have still worked the sense bound realities which are semblance, no more or no less than a semblance. And so we project atoms as the underlying materiality always projecting what we can weigh and measure into our outward realities. Its still a semblance.
The fascination of this semblance has actually improved man, for a time, as it is impossible to error within this semblance and the consequence is that the individual man is becoming or has become "free" for in working within this semblance he is becoming individual for there is no error in this realm.
The human soul is becoming a "free being" which not given to ancient man for in truth this "atavistic consciousness" was such that the human soul was still guided within the spiritual world where freedom is not evident within the individual man. When a man dies he is taken up into the spiritual world and is ensconced within higher beings who care for his progression. Man becomes a "free being" only on the earth, his schooling, so to speak. He can go from right to left, and sit or run, or jump for in this semblance there are no restrictions as to this basically free activity, the schooling of man.
"Freedom" and "semblance" go hand in hand for once within the world of the spirit man is a spiritual being who is progressing into an individual "free man" which will carry into the spiritual world as the human being brings "freedom' to the hierarchical beings with its concomitant "Love".
There is no human freedom within the spiritual world as each being acts within its particular manifestation, this "freedom" is the work of Man. We live within "illusion" because we cannot see the reality of the spirit to which our sense bound presentations are nothingness, the only reality being the spirit.
I'll go one more and state that the great "Fall of Man" from the world of the spirit via Lucifer began the world of our senses for the senses see "illusion', that Luciferic temptation but paradoxically it is the means for mankind to traverse into a higher being the Human Being all accomplished through recurrent lives. Lifting weights can be painful but strength and big biceps are the result.