The concrete world, far from being illusionary, is quite immediate,
relevant and approached by the capacities which exist within the soul.
The soul cannot afford to be passive because the world is participatory
in its essence and emerges out from it; darkness repress and separates it
from its light, conforming it into its own - this darkness, while emerging
out of forgetfulness is nevertheless part of the evil which is real.

The world, material conditions, the lower soul, the counterfeit spirit
and evil - while we may find ourselves to exist in a twilight between them and
the Pleroma - has such claim upon us that it is nonsense to speak of any kind of illusion.

An illusion is some phenomenon which briefly, or in a period of extension, appears

to be real, to be "solid" - in terms of the language applied by our positivistic empiricism inherited from the thinkers of the age of enlightenment and their successors in philosophy - but which, and this is important, reveal themselves to be unreal, to be a fabrication forged by the senses, by faulty interpretation of such, or as a cluster of beliefs which in a brief period of disorientation manifests itself as immediate, solid and verified by perception. "Illusion" as a figure of speech isn't even a valid argument for or against any phenomenon, deattached from perception and the interpretation of perception.
It is impossible for you to sit down in your chair, turn your computer on, log onto the internet and open this blog, and read these words - without this sequence of events, and your interaction with certain apparatus - apart from the world of matter.

This is observed also by the Gospel of Phillip, which argues that the resurrection will occur to a body, and this body is also matter :

But tell me what will rise, that we may honor you. You say the Spirit in the flesh, and it is also this light in the flesh. (But) this too is a matter which is in the flesh, for whatever you shall say, you say nothing outside the flesh.

So this flesh goes to destruction with all things that go to destruction - what rises out of the earth, given time, will return to it. In the meantime, as I addressed earlier, the Soul embodied continues to be sacrifice on the part of all incarnate life. There will be comprehension, there will be understanding,there will be wisdom, there will be knowledge - and there will be Gnosis - in the body, in the flesh, with you now, that you are living -
but the body goes to back to its own, leaving behind comprehension, leaving behind consciousness, leaving behind the mystery of breath. So it is true, the concrete, physical
world, with all its matter, with all its limitations, with all suffering - all unions and all separations - will not last, it is not eternal. But it is not an illusion, in any capacity.

About the proper attitude towards matter, the Gospel of Philip says "Do not love it, and do not fear it" - either way it detains you and substract from you what is
needed elsewhere, by way of emotion and disposition. This dispassion with
regards to it is made possible by not being centered within a conscious
center within us whose balance is towards "flesh" and "appearance"(untruth), it might be pertinent to speak of it as the body insofar as the manifest body is a form with which we are accustomed to. If we are too disposed towards the physiology and anatomy of ourselves and others, to the degree it overshadows all else, we grow morbid -while we
loose ourselves in these things - sensually, intellectually, creatively -
notion does not escape us that this appreciation itself does not repair
its condition, which is dwindling.

The Gospel of Thomas has Jesus diagnose the "rude awakening" of one which formerly thought to know and possess the body; "when you have found the body, you have discovered a corpse".
I do not mean with this that the Gnostic dualism has to do with body vs.
spirit, for there is a tripartition of man`s priority or
consciousness-of-self within most Gnoses within the Gnostic tradition, and
the three can never achieve status as dual or duality - also a tripartite
nature of the human being - his creation or coming into this particular form
you and I have - speaking of all qualities within the former three; has
also three stadiums and natures - the dualism of Gnosticism is Spiritual:
There is Pleroma and Kenoma; Fullness and Emptiness, there is Light and
Dark which are directly relating to the acquisition of Gnosis - moreover,
and this anchors the Initiatory, progressive, calculated approach of the
Gnostic Systems; wherein the Myth of Descent and Ascent, Fall and
Redemption, Forgetting and Remembering, Exile and Return plays a
significant part - namely the divide which exist between Spirit and
Counterfeit Spirit.

In the progression of the Gnostic Myth, Sophia produces an unequated reflection upon herself apart from the wholeness - while man is disposed to do so from the
beginning of his life on earth, enforced and encouraged by wellmeaning
mediators and tutors, by parental upbringing to education and religious
instruction - this also occurs in his soul. As such, he receives that
which is excreted out of Sophia, a particular portion of the Demiurge
containing his essence, and becomes its container, for most, for the
duration of his life.. whereupon the lion briefly roars and instills fear
in the souls of this aeon, only to again be brought down into this abyss
of purificatory preparations of Man interior.

In one liturgy we are informed Sophia bears twins, this becomes a subject
for both the Zervanite story of the younger and elder son, wherein the
younger coming to realization that his destination is subservience, breaks
through the womb before his brother and waits there to strangle him at his
arrival - and the medieval Cathar story of the sons Jesus and Satanael,
born to the unknown Dyadic "Father".

The Myth speaks to no-one else but the soul, that means, not the soul in
general, but yours and mine. If we are fulfilled in a greatly focused and
discerning consciousness coupled with all-embracing compassion for all
life, and particular that of our fellows who suffers the same from the day
they enter into the world, we may, through this really extraordinary,
almost unique ,.disposition, make do without it or similar reminders. But
the world is full of effective and ineffective, true and counterfeit
"myths" addressing souls in this capacity, and Tradition more often than
not are anchored with it, but often, so deep no "traditionalist" is aware
of it and cultures are bereaved of its benefits.

Christ is called, in some Christian traditions, "Second Creation" or even "Second
Nature" - it is Christ, in the selfsame, who collects and brings
together - the "Christian" himself/herself becomes the embodiment of this Second Creation and receives it; in one capacity as Adam, meaning the virgin "earth" which
receives it (whose symbol the Cross and essence the Ashes, are drawn upon
many brows on this day without any realization of this) - another
capacity, active, as Sophia, who in iconography is the "pregnant Madonna"
bearing within her the complete Christ (here pious Christian Ikons
actually depict a Docetic Christ who arrives completely formed and
transfigured out of Mary, but in a manner of revelation rather than
fleshly form) encircled by a Vesica Piscis, a Mandorla, a "womb of light".

While Catholics, ironically the most bitter polemists against Gnosticism,
Modern and Ancient, today - thinks that the Gnostics lived in fear of the
flesh and matter, thinking it to be the essence of evil contradistinct to
an entirely divorced reality of spirit; they still look toward the
Nativity on December the 25th as an answer to the fall of man into a
predicament which equals the fragility, vulnerability and nakedness of all
flesh, and simultaneously offers thought to the "forebears" earthly Adam and
earthly Eve, and essentially all mortal men and women proceeding from them
by the generations -and their fall into this condition which is what has
been diagnosized as the same by their "rivals and enemies" the Gnostics;
they still apply words pointing hope in the direction of a reintegration
into the Kingdom of God, following the ascent of Christ, in Christ and
through Christ, as well as a contemplation on the tomb of a man who was
born in the sight of other mortals, "laying with him in his tomb, entering
our death through his". All that is lacking is an appreciation that the
finitude of "creation" is a beguiling lie, and the architects of the
notions have for all too long forget the reasoning behind their craft - to
glorify the temporal as eternal. I.e. Idolatry.

If we possess a notion of Idolatry - the notion of a representation,
wrought by human hands, receiving the glory and worship True divinity,
True deity deserves; we acknowledge the Duality of types, and the
possibility of having a relationship towards true, revealed Reality
contra distinct to the false and contrived appearance of Reality.

There is no both and same in Gnosticism; at best we may be reminded of
existing things by inspecting what is "before our eyes", as the Gospel of
Thomas reminds us ; if we "cleave the wood, lift the stone" - we will see
what is hidden within_and hidden beneath; but this requires a certain
type of seeing, which only one certain type of eye might see.
This requires something else than passive certainity.

Before anything can be received into me, I must make sure I am the
space which receives it; it demands an emptying, and a complete
disrobing. In the same way, the verified authenticity of any world,
any being, any thing - depends on there first being a verified authentic
self. If there is any doubt, we must go where it leads, and open up
that about which there is any doubt. In the case of our self, we need
to be able to empty ourselves completely of everything preconceived,
everything that has accumulated without consent, without knowledge -
of that which we know is whole.