Illusions can be directly attributed to redundant concepts the collective human mind has accumulated in its efforts to understand reality. These concepts as they continue to be in force, muddle up the human mind's further attempts to elucidate reality.
Illusions emerged and are propagated by the mental constructs human individuals create/d in order to understand nature's workings mainly by philosophy. In the myriads of concepts which they do not have a foothold in reality. Of course human individuals have employed their imagination in order to understand reality. This led/leads to the creation of abstract entities and rules of practice in order to be able to expand beyond a limited area. Being consistent, as what has been contemplated in the past had to be the starting point for what to be contemplated in the future. Need of continuity.
But the final goal is the elucidation of a particular process and the concepts needed to do so are finite and specific. That means a lot of the concepts invented need to be abandoned, their use being temporary, products of a transitional stage. Once the main concepts have been defined, the redundant concepts are not needed anymore. Their use obsolete. This can be seen in the words, that even in every day life have gone out of fashion, become forgotten and discarded. The same goes for models that redundant concepts have built and have been employed to explain natural phenomena.
In what is known as a paradigm shift, old ways of thinking, collective or individual, are completely abandoned, erased from memory never to be visited again, utterly overwhelmed by new ways of thinking, new ideas. When paradigm shifts happen to single individuals the change is so complete the old ways of thinking lapse into oblivion. If by any chance the old self appears, in whatever way at any point after, is confronted with disbelief. Old ways of thinking seem alien to the point the individual wonders how was it possible to have embraced such ideas and does not recognise itself.
In the book of Bill Bryson, 'A short history of nearly everything', there is an account of ways of thought, widely accepted, that have been abandoned. It was in 1796 that Georges Cuvier put forward for the first time a formal theory of extinctions.
"His belief was that from time to time the Earth experienced global catastrophes in which groups of creatures were wiped out. For religious people, including Cuvier himself, the idea raised uncomfortable implications since it suggested an unaccountable casualness on the part of Providence. To what end would God create species only to wipe them out later? The notion was contrary to the belief in the Great Chain of Being, which held that the world was carefully ordered and that every living thing within it had a place and purpose, and always had and always would. Thomas Jefferson for one couldn't abide the thought that whole species would ever be permitted to vanish (or come to that, to evolve)."
Deep-rooted religious beliefs were at question there. At the beginning the idea that whole groups of animals were repeatedly wiped out and replaced with new sets were ignored, resisted, mocked and ridiculed. Charles Lyell, who geologists admit as the father of modern geological thought allegedly said:
"Never was there a dogma more calculated to foster indolence, and to blunt the keen edge of curiosity."
Though it was he who proved to be calculating in that matter, despite what he has contributed for the advance of geology. And it wasn't until the 1980s that the theory of extinctions finally won and the old ways of thinking abandoned:
"It is a testament to the strength of Lyell's sway that in the 1980s, when geologists had to abandon just a part of his theory to accommodate the impact theory of extinctions, it nearly killed them."
In the same way have been abandoned and if not any remnants still lingering in the minds of people should be wiped out leaving no trace at all, are concepts that stirred the hearts and directed the lives of many people. Concepts which have been used to erect huge artificial divides among groups of people, nations and their use brought only strife and destruction.