In the world of physical complexes, bodies are characterised by a definite and stable regularity of their external and internal relationships.
A table is in front of you. Your perception of the table changes with each varying position of your head. It disappears if you turn away from it or leave the room. But the table, as a body, does not change under these circumstances and remains in its place.
You can arbitrarily, by the effort of concentration alone, recall the psychical image of the table and place it in a series of other psychical images in the most varied associations of forms, but you cannot, in the same way, arbitrarily, by an act of will, make that table appear in a series of other bodies or in a new correlation with other bodies.
The interconnectedness of phenomena in both cases is different. In the physical world, it has a much more specific nature; it is exempt from any wilful caprice and is independent of fortuitous changes in the state of our organism. In the psychical world, phenomena appear as specifically dependent precisely on the state of the organism and proximally on the nervous system.
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BOGDANOV, A, 2020. Empiriomonism: essays in philosophy, books 1-3. Chicago, IL: Haymarket Books. ISBN 978-1-64259-348-8.