The most interesting of her essays are those which explain the system to which her editor Dr. Robert Lewins gives the name of Hylo-Idealism. This is described as the "brain theory of mind and matter," and it is so described because it asserts that every man is the maker of his own cosmos, all his perceptions having merely a subjective existence and being generated by the brain, "which focuses converging rays of sense from all parts of the body, and unites them into the white light of consciousness." It would be a mistake, however, to think that, according to this theory there is nothing outside of the percipient subject, that is, beyond man himself. The real existence of matter is not denied and, indeed, "so far from being a nonentity, matter is the _fons et origo_ of all entities." Hylo-Idealism deals only with the relative, "ignoring the absolute as utterly beyond human _gnosis_." While asserting that "the only cosmos known to man, or in any way concerning him, is manufactured in his own brain-cells," it affirms the existence of another cosmos, the external universe of other systems. The mind does not however passively apprehend external objects, but actively constructs them. "We make the mountains, and the sea, and the sun himself; for sunshine is nothing if not visible, and if there were no eye and no brain, there could be no sunshine." The defect of this reasoning is that it makes man the only measure of all things. Because our senses are necessary to us to distinguish certain phenomena, it does not follow that the same phenomena cannot be distinguished under other conditions. The protozoa which have no organs of special sense are affected by the vibrations of light, sound, and probably smell, which would not be possible if those phenomena are "constructed" by the human mind.