The phrase "pure invention" means something that is completely made up or created from the imagination, without being based on any reality or truth. Full definition
That they started in the 1820's does not take away from the fact that what they base their dogmas upon is pure invention on the part of a somewhat deranged preacher (who even claimed to walk on water... disproved, fortunately). (religion.blogs.cnn.com)
It is pure invention in colour of a very high order, and the light that is generated through the juxtapositions and adjustments of colour and tone is as unnaturalistic as the best Klees. (abcrit.org)
Creativity is rarely about pure invention. (brainygamer.com)