Unless, of course, we are all zombie manifestations

Question

What does the specified sentence mean? How can it be rewritten without "unless"? I can not understand the role and meaning of "unless" here.

Context:

But in reality he has still not resolved the Cartesian mind/ body dilemma for though Lucy is made manifest physically – from aluminium with hair and fabric – she is essentially virtual and her sensations are synthetic. So that she may ‘feel’, the chemical processes that are intrinsic to human emotions are mimicked, triggered by an interaction with the environment certainly, but processed through computerised differential equations – dry code, not wet chemistry. This may result in an exact simulacrum of human responses and behaviours but it might be difficult to determine whether Lucy can become a real and fully conscious being rather than a cleverly constructed zombie. Unless, of course, we are all zombie manifestations of virtual instructions? While Steve Grand is building Lucy one neuron at a time, some neuroscientists can see the potential to extend the capabilities of our existing brains.

Answer 1

The author refers to one of the central problems of philosophy, which AI researchers are constantly tripping over and being surprised by. In the previous sentence, he mentions the difficulty of knowing whether 'Lucy' is a genuinely thinking being or merely a clever copy, able to pass a Turing test but having no existence independent of her programming. But wait a moment (thinks anyone who has seen The Matrix) - how do I know whether anybody is a human being or just an AI in a realistic body, given the illusion of sentience by the programmer?

Descartes suggested that all our sensations might be deliberately falsified by demons: as neuroscience became more than witchcraft the suggestion was that we may be disembodied brains in tanks, part of some biological experiment on one of the planets of Alpha Centauri: when I was a student and considering programs like ELIZA, the daring suggested that we may in fact be programs ourselves. Personally I take the commonsense view, a compromise between Rationalism and modified Intuitionism - I know I am a human being by inspection, and am willing to give the rest of you the benefit of the doubt out of politeness.

So your sentence means approximately "But there is always the possibility that there is no such thing as 'a real and fully conscious being rather than a cleverly constructed zombie'; we may all be zombies".