Father Geoffrey Korz on Gnosticism

The Orthodox Church recognizes that Christ is God Who took on human flesh, and sanctified all creation. As such, Orthodox Christians reject the idea that any physical object is inherently evil or sinful; this is particularly true for any sanctified person, place, or object, in which the grace of God dwells. This is the reason the Church blesses objects, consecrates church properties, and ordains (sets aside) some men for the priesthood: to gain a unique grace from God. Rejecting these sanctifying practices of the Holy Church, handed down to us from Apostolic times and confirmed by all the Ecumenical Councils, is a particularly obscene form of the heresy of Gnosticism, which rejected the physical world as corrupted, and held only invisible “spiritual” things as potentially holy.

Spiritual things would include angels and "spirits" (and as such, demons), disembodied voices uttering prophecies, and revelations of knowledge through the mind. To a gnostic, nothing in the physical world can ever be blessed, sanctified, or made holy - this is the reason they reject Christ God coming in the flesh. All these things have been formally condemned (and repeatedly re-condemned) by Church Councils.