It seems that the meeting place for material and immaterial forms in human life and history is a zone of controversy. In the history of Science, for example, neither "the ether" nor gravity have ever been found to have either a physical body or to exhibit mass (lets ignore the controversial 'graviton' for ease of conversation). Yet both act as fundamental concepts, the ground on which much of the science of their (in the case of the ether) or our (in the case of gravity) rests. A change in belief as to the fundamental nature of these concepts, themselves fundamental, offers many new perspectives not believed to exist if not a complete shift in the shared predominant worldview, the 'reality' of science. Concepts moving from substantial (material) being to non-being (immaterial, insubstantial being) thus create quite a stir. Yet formally of course, they still exhibit structure much as material objects (mathematics, for instance, can be expressed entirely conceptually- this is the very nature of its existence. Yet, as pointed out in earlier essays, it, for all its mass-less-ness it has no lack of structure, but that is a different conversation).
It is interesting to note that before their redefinition, reevaluation, or replacement by other objects on the border between form immaterial and material that concepts held to be the fundamental ground on which systems of ideas are based function not only to support ideas but also as a barrier, or fence over which the imagination has a difficult time reaching. This is basically the converse of the idea in the last paragraph: the REASON that a change in belief regarding the structure of an idea between material reality and immateriality is often such a breakthrough (or alternately controversial) is that what is being tested is the limit of what was thought to be possible, even as a conception. Thus conceptual borders, fences, assume physical behavior in terms of what can be believed to be possible.
Also worthy of consideration is the strange power which energy in this transitional space takes on. People start WARS because of such shift in ideas. Religions, with all of the strife, oppressive behavior, magnificent architecture, civic organization, and mass movement of people that they inspire, require, effect and so forth have no mass! They are just concepts, and they clearly illustrate a pivot between the material and immaterial world. In fact, in many religions it is a gesture from a spiritual immateriality that granted existence to material suchness! Of course, though many people also feel that this evolution happened in the opposite direction, it cannot be denied that this point of transmutation, transmigration, or transmediation (whatever they call it) between the material and immaterial worlds of form and vice-versa (if one considers religions whose goal for the individual after death is a paradise- thus movement from material to immaterial form) serves as a center of motivation within a particular aggregation of individuals, an intense bond of unity capable of momentous action.
In this way shared immaterial forms container at the very least function in the material environment of material forms for the population which shares them. Despite the fact that this process is itself mental, some of these forms can function on a metastructural level, underlying basic thought processes resulting in assumptions as to the nature of existence shared by a collective population. These assumptions are strong enough to influence even individual perceptions of 'real' objects, to place the previously mentioned boundaries around the imagination (which, to be fair, might not be able to function without them) and effect even the ground of collective thought believed to be empiricist in nature. Thus immaterial forms can serve to control the aggregate if seen from a wider view (in a psychologically fascist sense). Of course, the same ideas can be seen to be the result, rather than the cause, if this process is viewed in reverse, as an (unconscious?) collective democracy, actively participating in the creation of their reality.