The material and the ideal are two aspects of the same thing.
I notice you ask for "proof" both here and on the "spirituality" thread, but at this level of discourse the very nature of "proof" is open to deconstruction because "reality" is itself being negotiated. Even scientists do not look for "proof" as such, only for best -fit explanations which are "falsifiable in principle".
It was not my point, but there are at least two reasons why "body"
and "mind" shoud be considered as unified.
(1) If they belonged
to different levels of existence there is no mechanism for interaction.
(Descartes needed to evoke "God" for providing the linkage)
(2) What we consider "material" is merely a concept
subject to our everyday sensory experience.
What is "solid" or "permanent" to humans is relative our physiology and lifespan.
In fact all matter is an illusion E=mcsquared. Matter and energy are interchangeable. Existence and consciousness are conceits brought about by Evolution.
The problems of "existence" cannot be solved by traditional logical/mathematics since such logic is based on static set theory which already assumes the existence and permanence of "things" independent of observers. and ignores the dynamics of relationships (i.e. the fluidity of "set membership"). Philosophically, this is a basis for "naive realism".
Some progress has been made in formalising the issue , for example, using a "systems theory" approach (see e.g. Capra "The Web of Life") but such a shift requires a re-examination of epistemological issues such as what is meant by "explanation". In general ontology (theories of existence) and epistemology (theories of knowledge) are inextricable from each other.
meaning is an another illusion, you are try to anthropromorphasise the universe